The working principle of ultra high pressure common rail system was introduced, the intake port and combustion chamber simulation models were built respectively with Fire software, and the effects of matching relationship between air, fuel and combustion chamber parameters on engine performance were then analyzed. It provided the theoretical evidence for further improving engine performance and optimizing the parameter matching. The results show that the larger swirl ratio within the range of 1.21 to 3.62 at the same nozzle diameter is more beneficial to improve engine performance and the effects of larger nozzle diameter are more effective under ultra high pressure injection conditions. When the swirl ratio is 3.62 and the nozzle diameter is 0.30 mm, the highest brake mean effective pressure and the optimal emission effect can be achieved. The smaller combustion chamber aperture ratio at the same nozzle diameter is more helpful to improve engine performance and the smaller nozzle diameter will strengthen the effects. When the combustion chamber aperture ratio is 0.75 and the nozzle diameter is 0.23 mm, the best dynamic and emission performance can be acquired.