Abstract: To study the method of setting up the reliability models of the state control circuit of electronic safety and arming devices system(ESA), the time domain analysis was used to divide the system into some operating sections effectively. The safety and reliability models of the circuit were set up by using a computer to simulate the effect of the faulty components on the safety and reliability of the circuit. The method fo time domain analysis solved the question of building the reliability models of complicated sequential circuit, which lays a good foundation for further research on the reliability of ESA.