In many spaceflight measure and control software systems, varieties of measure data are exchanged between different software. Qualities of measure and control software systems are influenced by the performances of data exchange software greatly. Many problems that appear during the running process of real-time measure and control software and are difficult to be located are caused by data exchange software. So, it is necessary to analyze the performances of data exchange software while designing measure and control software systems. In this article, the Petri net model of the real-time data exchange software is established first. Then the model is simplified and analyzed. The design of abnormity control for buffer overflow is given. Finally,using the Petri net method, the performances of the real-time data exchange software are analyzed and discussed.