Two-dimensional (2D) layered metal dichalcogenides have attracted extensive attention due to their unique physicochemical properties, such as high carrier mobility, strong light-matter interaction and tunable band gap. Tin disulfide (SnS₂), as an emerging 2D layered metal dichalcogenides with a narrow band gap (2.0~2.6 eV), has a CDI₂ type crystal structure and the layered structure is formed by a stack of sandwiched S-Sn-S planes connected by van der Waals force. Furthermore, SnS₂ is non-toxic, low-cost, and storage abundant, which meets the need of industrial production of electronic and optoelectronic devices. It also exhibits excellent photoelectric responses such as high absorption coefficient (α₀~10⁵~10⁶ cm^-1), large on/off ratio (>10⁶), high carrier mobility (230 cm² V^-1S^-1), and so on, which ensures its rapid development in photoelectric applications such as photodetectors, solar cells and photocatalysis. However, so far, research on the nonlinear optical properties of SnS₂ films is still in infancy. In the early stage, SnS₂ was prepared by liquid phase exfoliation technique to firstly explore its nonlinear optical properties. The SnS₂ films always show saturable absorption under the lower photon energy than band gap. This saturable absorption can be explained by some surface defects, coming from the growth process. As such, many novel 2D semiconductors such as WS₂ and MoS₂ with S vacancy defect also have been demonstrated and successfully applied into mode-locked, Q-switched, and other photonic devices. The defects can capture excitons, electrons, and holes to modulate nonlinear absorption. Thus, it is necessary to confirm the defect type and then systematically analyze the nonlinear optical response of SnS₂ films. Compared with horizontally aligned 2D film, vertically aligned materials have larger specific surface area and exposed edge sites, thus resulting in higher light absorption characteristics. Furthermore, the active edges of MoS₂ have shown a strong resonant nonlinear optical susceptibility and the vertically aligned WS₂ shows higher modulation performance. Thus, it is crucial and meaningful to prepare vertically aligned SnS₂ layers, which are promising to exhibit an excellent nonlinear optical property. Recently, vertically aligned SnS₂ layers have been successfully synthesized by hydrothermal method. However, impurity and surface roughness would provide a large contribution for the nonlinear scattering and result in sophistication in the mechanism analysis of nonlinear optical response. Herein, it is noteworthy that the controllable synthesis of vertically aligned SnS₂ layers is also the key to study the nonlinear optical response. Compared with liquid phase exfoliation method and hydrothermal method, Chemical Vapor Deposition (CVD) has been demonstrated as an effective and general method to prepare 2D film in large-area. In this paper, large-area SnS₂ films are prepared by CVD method using SnO and S powders as precursors and c-plane sapphire is selected as target substrate. The SnS₂ nanosheets are uniform and well-aligned on the c-plane sapphire substrate characterized by scanning electron microscopy. The average width of nanosheets is approximately 400 nm and the thickness of nanosheets is about 750 nm. X-ray photoelectron spectroscopy and Raman spectroscopy confirm the successful preparation of high-quality vertically aligned SnS₂ film. The effect of pump power on the nonlinear optical response of vertically aligned SnS₂ film is investigated at 800 nm by using open/close aperture (OA/CA) Z-scan technique. The results show that the vertically aligned SnS₂ film exhibits an obvious saturable absorption. This can be due to the S-vacancy defect single induced photon absorption and the corresponding defects are characterized by X-ray photoelectron spectroscopy. The calculated results show that the third-order nonlinear absorption coefficient (β) of vertically aligned SnS₂ film is 1-2 orders of magnitude larger than that of previously reported 2D nanosheets, and the absolute value of β decreases with the pump intensity, which is mainly contributed to the Pauli blocking effect. With the increase of incident laser intensity, electrons in the valence band are continuously excited to the defect state and transmitted to the conduction band until electrons and holes occupy nearly half of the photon energy in the valence band and conduction band. Due to Pauli blocking effect, the interband transitions are blocked and the saturable absorption response takes place. At this time, the relationship between total absorption can be expressed as $\alpha \left(I\right)={\alpha }_{\mathrm{0}}/(\mathrm{1}+I/I_{\mathrm{S}})$. More importantly, the modulation depth of vertically aligned SnS₂ is up to 50%, which provides a reference for designing high-performance nonlinear photonic devices. In addition, the nonlinear refractive index (n₂)_{of SnS2 film grown vertically is also measured, and the values of n2 also decrease with the pump intensity, which is mainly related to the free carriers and bound electrons of the material. Meanwhile, the n2for vertically aligned SnS2 film is comparable to previously reported 2D nanosheets, such as WS2, WSe2, MoS2, MoSe2, and MoTe2. Based on the above-analyzed results, we find that vertically aligned SnS2 film has a great potential in the design and manufacture of nonlinear photonic devices.}