The invention relates to an H.265 rate control method for an improved R-lambda model. The method comprises the steps that firstly, relevant parameters of the rate are initialized, and for current coding frames, the variance, the absolute error and the SAD value of each image are calculated; secondly, bit allocation at the GOP level is conducted according to the JCTVC-K0103 proposal, and the absolute errors and the SAD values are compared; thirdly, a key frame, namely an I frame is inserted, the relevant coding parameters of the rate are reset, coding is conducted in an I frame rate control mode, and then coding of the current frame is ended; finally, bit allocation at the picture level is conduced, and the relevant parameters of the rate are updated according to the improved type. According to the H.265 rate control method for the improved R-lambda model, at the same rate, the video quality is remarkably better than that obtained through an existing method, and the image quality is remarkably improved.