The invention is failure diagnosis method for injector of electric gasoline engine. It is mainly applicable for injector of electric gasoline engines with multi-point air intake injecting. When taking this method to diagnose, reference cylinder is set firstly to ignite the firing signal transducer on high-tension cable and the oil pressure transducer on gasoline distributing pipe. Measure the gasoline dynamic pressure in the gasoline distributing pipe by a computer, manage and analyze the collected date by diagnosis software and achieve the variation of oil pressure time-domain or wave component frequency-domain. Then, compare with the variable regulation when the injector working normally to judge there are whether failures of the injector. Fix position of the failure injector based on the position of the reference cylinder, the work sequence of the engine and the injecting regulation.