The preparation of high-quality perovskite films with optimal morphologies is important for achieving high-performance perovskite photodetectors (PPDs). An effective strategy to optimize the morphologies is to add antisolvents during the spin-coating steps. In this work, a novel environment-friendly antisolvent tert-amyl alcohol (TAA) is employed first to improve the quality of perovskite films, which can effectively regulate the formation of an intermediate phase staged in between a liquid precursor phase and a solid perovskite phase due to its moderate polarity and further promote the homogeneous nucleation and crystal growth, thus leading to the formation of high-quality perovskite films and enhanced photodetector performance. As a result, the responsivity of the PPD reaches 1.56 A/W under the illumination of 532 nm laser with the power density of 6.37μW/cm2 at a bias voltage of -2V, which is good responsivity for PPDs with the vertical structure and only CH3NH3PbI3 perovskite as the photosensitive material. The corresponding detectivity reaches 1.47×1012 Jones, while the linear dynamic range reaches 110 dB. These results demonstrate that our developed green antisolvent TAA has remarkable advantages for the fabrication of high-performance PPDs and can provide a reference for similar research work.