Abstract: As the difficulty of knowledge acquisition restricts the application of launch vehicle fault diagnosis expert system, a knowledge acquisition method based on test event graph was proposed. By setting a reasonable graphics components, drawing out the test event graph, it can well represent the testing process of launch vehicle, then designing the algorithm that can automatically translate the test event graph into the knowledge of expert system knowledge base. This graphical method can effectively simplify the difficulty of knowledge acquisition, and is easy to understand and use. Through the testing, this method has good prospect for engineering application.