The GB 12676-2014 （Technical Requirements and Testing Methods for Commercial Vehicle and Trailer Braking Systems） had been implemented on July 1，2015.The establishment of the supplement standard （GB12676-2014 Testing Method for the Retarder Braking System Performance of Commercial Vehicle） is the base for the technical and performance appraising of retarder. It will change the situation of lacking testing method for retarder in China and will play an important role in improving the standard system for Chinese auto braking and the braking safety of commercial vehicle. This paper mainly introduces the principal of establishing this standard and the analysis on the basic principal and testing method etc.. and provides the testing results and conducts overall explanation and analysis on the standard.