The technological process of guided missile defense systems(DSP) was analyzed, and the impact-point prediction and orbit determination of strategic missile theory based DSP satellite were proposed. Thus, with the mode of two satellites spaced, the measurement model of DSP satellite was put forward. In order to calculate the orbit of the missile, the dynamic model with multi-parameters of the powered phase and free section of the missile were created. For simplifying the calculation, the reduced dynamic model of missile was put forward in order to reconstruct the whole simulation of ballistic missile early warning system, which was ballistic determination and the impact-point prediction. Then the UKF filter algorithm was used to calculate the position and velocity of missile on real time. Finally, the simulation experiment based on STK was generated, and the results show that the impact-point prediction precision can be 10-50 km, which can satisfy the basic military requirement.