The performance of a piston internal-combustion engines is reflected by indicator diagram and indicator parameters. It is of great significance to evaluate performance, inspect quality, redesign and maintain internal-combustion engine by computing parameter and analyzing combustion according to tested indicator diagram. Aimed at two-stroke piston engines, a dynamic pressure test system of internal-combustion engines is developed with high speed acquisition devices, angle signal generators and pulse shapers. After a further research on the measurement of dynamic top dead center (TDC), the computer algorithm based on the p-ψ indicator diagram of TDC and the average indicator pressure is putted forward. With the application of the multithreading technique, dynamic link library technique and multi-document template technique, a testing software, which is credible and multi-purpose, is programmed. The experiment indicates that the indicator diagram and indicator parameters can be under accurate measurement with the testing system.