The invention discloses a video stream splicing method and system. The method includes the following steps that: SEI (Supplemental Enhancement Information) in splicing code streams is parsed; a dpb_output_delay value of spliced code streams is calculated according to the SEI, and the dpb_output_delay value, which is carried by the SEI is replaced, and decoding is performed according to the SEI, wherein the dpb_output_delay value which is carried by the SEI is obtained according to code streams before splicing. With the video stream splicing method and system of the invention adopted, problems existing in compatible consistency of an HRD (Hypothetical Reference Decoder) of the splicing code streams can effectively solved.