The improvement of environmental performance by gasoline direct injection (GDI) engine is remarkable. But the gas mixture formation process, which greatly affects the combustion of direct injection spark ignition (DISI) engines, still has a lot of areas left unclear. In this paper, a CFD model of air intake, fuel spray atomization and mixture formation process of a certain GDI engine was developed and experimentally verified for DISI injection study. The effects of injector spray layout and injection strategy on mixture quality of DISI engine were analyzed by respective simulation of three different injectors T1470, T1471, T1472. Results show that the mixture quality can be improved with appropriate injector spray orifices layout. Further simulation analysis show that, the impingement of the fuel spray on the cylinder wall or piston is reduced and the cylinder turbulent kinetic energy is increased by using two-stage injection instead of single fuel injection under condition of full load at low speed. In addition, the concentration of mixture near the spark plug is increased, and the quality of mixture is improved with more appropriate injection timing and injection fuel ratio of the first injection stage and the second stage.