To analyze the impact of hybrid gratings on silicon thin film solar cells, the crystalline silicon solar cells with mono shape of grating, syntropy and anisotropy shapes of hybrid grating were designed. And the thickness of silicon layer was unified. By finite-difference time-domain method, the optimal sizes, photocurrent densities and optical absorption of hybrid gratings were optimized, respectively. The results showed that the anisotropy hybrid grating had more optical absorption performance than other structures. Through analyzing the electromagnetic field intensities, the mechanism of optical absorption enhancement of hybrid grating structure was found. Also, the photocurrent density with different grating numbers of component structures was calculated for the anisotropy hybrid grating. Simultaneously, the optimum combination of a triangle convex and a parabola convex in anisotropy hybrid grating was quantified by the factor of absorption enhancement. By varying the ratios of width and height regularly, the photocurrent densities were calculated. Results indicated that the photocurrent density of the anisotropy hybrid structure increased by 62.9% relative to a flat solar cell when the ratio of width was set 1: 1 and the ratio of height ranged from 0.67 to 1.86. The study can provide a theoretical reference for the structure and parameter design of thin film solar cells.