An acquisition and analysis system for indicator diagram (ID) of piston engine is developed for monitoring the cylinder pressure in engine development. The hardware component of the data acquisition system is introduced. The method of the determination of the TDC, the method of filtering the interference signal of ID and the method of implementation with Visual C++ are presented. The system can provide ID online through the experiment on Honda 125 engine. It can directly and conveniently display the information about combustion. Therefore it has a high potential value in engineering applications.