a method for measuring audio and video synchronization error of an audio / video encoder system is provided . the method includes steps of : producing a reference video data having a first time length and including a particular image pattern and a reference audio data having a second time length ; inputting the reference video data and the reference audio data into the audio / video encoder system to produce an encoded video data and an encoded audio data ; processing the encoded video data and the encoded audio data respectively to produce a detected video data having the first time length and including the particular image pattern and a detected audio data having the second time length ; and detecting a first time point of an audio data of the reference audio data synchronized with the particular image pattern of the reference video data and a second time point of an audio data of the detected audio data synchronized with the particular image pattern of the detected video data by an analyzing tool , and calculating a difference between the first time point and the second time point .