The real-time parameter is a key point in PROFIBUS field bus protocol's performance evaluation, so how to analyze and count its communication parameter is of great importance. According to the problem, based on the detailed analysis of PROFIBUS field bus access protocol, a type of testing platform for PROFIBUS-DP communication performance is designed. Through this testing platform, these real-time performance parameters are analyzed including bag information rate, transmission efficiency, network average utilization, network throughput, transmission delay, token rotation time etc., and the relationship between bus cycle time and master station or packets number are also given out. So, the real- time performance of PROFIBUS-DP is quantitativly analyzed.