In order to make full use of the air in the chamber, improve the mixing process, and reduce raw emissions and fuel consumption of diesel engine, we introduce the the concept of a new combustion systemthe Double Swirl Combustion System (DSCS)and introduce their hypothesis regarding the fuel-air mixing mechanism under DSCS. For validating the hypothesis, we made a series of actual diesel engine tests on DSCS. The engine tests were based on a 150-mm diesel engine, and both single-cylinder and multicylinder engines were tested under natural aspirated intake condition and boost intake condition. The results indicate that DSCS is suitable for improving a big bore diesel engine. Later, we made a series of spray experimental researches in order to investigate DSCS and whether it can be used under different load conditions. In addition, we investigated how the structural parameters of the DS chamber affect the fuel-air mixing process in order to establish an optimum design method of the DS chamber. In order to verify whether DSCS can be used in different types of diesel engines, we made a series of engine tests on a 132-mm diesel engine. Results indicated that DSCS also can present a wonderful performance on medium bore diesel engine. For phenomena of 150- and 132-mm diesel engines' performance by matched DSCS, we suppose there exists necessary to make a further research on DSCS from the microcosmic level. Therefore, we made a series of simulations on 132-mm DS and the 132-mm original chambers. From the simulation results, they obtained meaningful results from the velocity field and temperature distribution comparisons. The results we obtained validate that DSCS has many advantages, such as a diesel engine with an ideal heat release rate, a better fuel economy, a lower emission, and a lower thermal load, all showing potential and a bright future for DSCS owing to the wide application of electronic-controlled fuel injection systems.