With a aid of electronic controlled fuel injection system, a method of fault tree automatic construction was described, which based on the formal description of fault tree constriction.Using directly existed components’ and identifier’s model library, the method could synthesize fault tree automatically according to the specified top event and its state. The omission of incident was avoided, and the complex loop of the system could be processed directly according to the standard, so that the work efficiency was improved. No traditional personal errors, the accuracy of construction was high.It has practical significance for tracing the root cause of the system’s polymorphic faults, and further facilitates the reliability analysis of the system.The method is also widely applicable for other automatic system construction of fault tree.