This paper is based on MATLAB software and conducts mathematical modeling and simulation calculations of an engine equipped with a double rotary valve cylinder head assembly, which was developed by the project team. Structural parameters were selected based on the size of the prototype that had been tested, and the working process inside the cylinder was modeled and simulated. The simulation results were analyzed and compared with those of the original poppet valve engine. The results indicate that the intake endpoint pressure and the maximum burst pressure of the rotary valve engine are both improved compared to the original engine. This study provides a method for calculating the intake and exhaust processes of the rotary valve engine and can provide a reference for the matching of the rotary valve cylinder head assembly with various types of engines in the future. These results may contribute to improving the design and performance of the engine to meet the needs for higher efficiency and lower emissions.