A method for optimizing a second coding is provided. The method includes: Setting a quantization parameter of a start frame of a video sequence according to a range of an input quantization parameter QP0 of a coder; performing first coding with a simplified method, and calculating a frame-level temporal impact factor ki of a current frame and a block-level temporal impact factor kB,j of all 16×16 pixel blocks in the current frame; restoring reference list information of the coder after the first coding is completed, and then determining whether a scene is switched; and performing the second coding by setting quantization parameters with different strategies according to whether the scene is switched.