In the simulation of the ballistic missile defence system, the trajectory of tactical ballistic missile needs to be simulated. Generally, the trajectory of short range ballistic missile can be considered as parabola, while the trajectory of long range ballistic missile can be considered as ellipse. According to the deferent characteristics of those two types trajectories, deferent simulation models were built, each had three distinctive phases (boost phase, ballistic phase, reentry phase). This model can provide a better operational object in the distributed simulation system of missile conflict, and enhance the creditability of the simulation result.