Reliability of CTCS-3 train operation and control system is necessary to ensure train running safely and efficiently. Thus, train control system simulation should be used for lots of tests and validations. This paper is focus on the theory and period of fault injection systematically. According to characters of simulation of train control system and advantages of fault injection, application of fault injection in the field of train control system simulation is proposed for reliability test and to obtain system information after fault injection. Main structure and detailed functions, structures of fault injection system is designed and realized. This system could simulate system fault to cause rapid failure in train control system during the experiment. By analyzing the simulation result, the conclusion could be obtained that application of fault injection could help to improve reliability and fault tolerance of C3 simulation.