A method for processing video and audio data received in a decoding system, comprising: recovering a system time clock by using a presentation time stamp of video or audio data when a program clock reference is unavailable in the system; comparing the STC with the PTSs of the received video and audio data currently captured; and, if the PTS of the received video or audio data is greater than the STC the received video and audio data are buffered, if the PTS of the received video or audio data is smaller than the STC the received video and audio data are discarded and if the PTS of the received video or audio data is equal to the STC, the data is determined to be played back, further comprising subsequently monitoring the difference between the PTS of the video data and the PTS of the audio data to be played back; and comparing the absolute value of the difference with a set threshold value, and adopting an asynchronous play mode as a system play mode when the absolute value is greater than or equal to the threshold value; adopting a synchronous play mode as the system play mode when the absolute value is smaller than the threshold value; wherein, after the system is switched to the asynchronous play mode, the STC is no longer compared with the PTS of the video data and the PTS of the audio data to control the processing state of the current data and the presentation time of the current data, further comprising: after the adopting the asynchronous play mode as the system play mode, switching the system to the synchronous play mode when monitoring that the absolute value of the difference is smaller than the threshold value during a set time period; maintaining the system in the current asynchronous play mode when monitoring that the absolute value of the difference is greater than or equal to the threshold value and set time is not reached; or after the adopting the synchronous play mode as the system play mode, switching the system to the asynchronous play mode when monitoring that the absolute value of the difference is greater than the threshold value and set time is reached; maintaining the system in the current synchronous play mode when monitoring that the absolute value of the difference is smaller than or equal to the threshold value and set time is not reached, wherein after the adopting the synchronous play mode as the system play mode, the method further comprises correcting the STC by using the PTS of the video or the audio data. recovering a system time clock by using a presentation time stamp of video or audio data when a program clock reference is unavailable in the system; comparing the STC with the PTSs of the received video and audio data currently captured; and, if the PTS of the received video or audio data is greater than the STC the received video and audio data are buffered, if the PTS of the received video or audio data is smaller than the STC the received video and audio data are discarded and if the PTS of the received video or audio data is equal to the STC, the data is determined to be played back, further comprising subsequently monitoring the difference between the PTS of the video data and the PTS of the audio data to be played back; and comparing the absolute value of the difference with a set threshold value, and adopting an asynchronous play mode as a system play mode when the absolute value is greater than or equal to the threshold value; adopting a synchronous play mode as the system play mode when the absolute value is smaller than the threshold value; wherein, after the system is switched to the asynchronous play mode, the STC is no longer compared with the PTS of the video data and the PTS of the audio data to control the processing state of the current data and the presentation time of the current data, further comprising: after the adopting the asynchronous play mode as the system play mode, switching the system to the synchronous play mode when monitoring that the absolute value of the difference is smaller than the threshold value during a set time period; maintaining the system in the current asynchronous play mode when monitoring that the absolute value of the difference is greater than or equal to the threshold value and set time is not reached; or after the adopting the synchronous play mode as the system play mode, switching the system to the asynchronous play mode when monitoring that the absolute value of the difference is greater than the threshold value and set time is reached; maintaining the system in the current synchronous play mode when monitoring that the absolute value of the difference is smaller than or equal to the threshold value and set time is not reached, wherein after the adopting the synchronous play mode as the system play mode, the method further comprises correcting the STC by using the PTS of the video or the audio data.