Yet the nozzle of fuel injector for Gasoline Direct Injection (GDI) engine exposing to high temperature combustion gas and soot makes it easier for deposits to accumulate on. Even in the earliest publications about GDI system the risks of deposits formation on injectors were discussed [5,6]. Additionally, the impact factors and mechanisms of deposit formation were also described in many papers [1,6–13]. The injector tip temperature, fuel composition and nozzle geometry including its surface characteristics were considered the main impact factors of deposit formation in these literatures, yet the mechanism has not been completely understood. To the effects of deposits have on injectors and engines, it’s known to all that deposits forming in injector orifice could both restrict the fuel flow and alter the spray characteristics of the injectors, and the influences of fuel flow decrease and injector spray distortion on combustion in cylinder [8,14] and on fuel consumption, exhaust emission, particulate as well as drive-ability [7,14–19] were also demonstrated. However, the exact effects of deposits on spray behaviors, or to what extent deposits impact on spray behaviors, were barely seen. The paper by Lindgren [20] had provided some description on the difference of sprays between a clean injector and a fouled injector using spray visualization technologies. His findings showed that the pre-jet of the fouled injector was more dense and penetrated faster and the mean drop diameter was 5% higher compared to a new injector. However, it is believed that ‘‘more optical studies should be carried out to provide a better understanding of the spray”...‘‘for fouled injectors, including all injectors types” [21].