The technology of water injection for gasoline engine has become a new research hotspot in recent years because spraying water into combustion chamber can reduce knock tendency and improve fuel economy and emissions. The spray characteristics of water injector were first studied through the experiment, the scheme of water injection inside the intake port was designed with CFD method based on a 1.5L TGDI engine, and the bench test was finally conducted at 3000 r/min with 1.4MPa and 5500r/min with WOT. The results show that the water injection can reduce knock and improve fuel economy effectively. Water injection can decrease the exhaust temperature and realize the equivalent-ratio combustion instead of rich fuel strategy under the conditions of high speed and high load.