Based on a 4 cylinder turbocharged diesel engine, the research aims at studying the influence of some the fuel injection timing, fuel injection pressure and the ratio of pilot injection fuel to the engine combustion and emission formation under the condition of single injection and pilot injection ,respectively ,which the main focus on the emission characteristics of particles .The results show that the early-injection PPC formed by single injection can reduce the quantity and quality and GMD of particles obviously. However, when the injection timing is too early, the quantity of particles will rise as normal mode. The effect of injection pressure on particles is significant. The quantity of particles will increase under the condition of PPC, but the quality and GMD of particles is first decrease and the increase. The curve of size distribution of particles displays three peaks shape. Generally, there are two stages of heat release in the pilot injection combustion, and the exothermic peak position will not change with the variation of the ratio of pilot injection fuel, which is called cold flame reaction. In general, the pilot injection can reduce the soot emission dramatically. However, if the timing of the advance to a certain value, the quantity and quality and GMD of particles are almost unchanged. Increase the proportion of pilot injection fuel to form a higher proportion of premixed combustion, the quantity and quality of particles can be decreased, GMD is increased first and then decreased. When pilot injection fuel is injected into the cylinder, the temperature and pressure in the cylinder is low, thus the fuel burning rate is slow and the combustion is not complete, meanwhile some intermediate products will be generated. Therefore, the HC and CO emission will increase at the same time.