Aiming at the availability assessment of missile weapon system which the life function or the time of maintaining incomplete obedience exponential distribution and is unsuitable for Markov model. The availability model of missile weapon system considering delay time, maintenance time and series repairable is established by using renewal process, and a demonstration application is conducted. The calculating example result is approach to the simulation result. It examined the model possibility and valid methods for availability analysis to non-Markov system.