Low temperature combustion (LTC) based on two stage injection was achieved by using main injection to generate homogeneous charge and trigger injection to ignite. The effect of main to trigger injection ratio and the start of main injection (SOMI) on the LTC was studied. The result shows that the trigger injection can control the start of combustion and make the LTC more stable. Using the trigger injection can effectively broaden the range of the SOMI. The SOMI is quite important for the LTC. Main injection timing too early or too late will deteriorate the performance of the LTC, resulting in high emissions. Optimizing the SOMI for different main to trigger injection ratios can control the process of combustion and emissions.