Through this paper, we propuse appkication of TDOA- Trilaterartion Algorithm for detect position and trajectory of ballistic rocekts on secondary radarv system. Technique for get distance between transceiver station and transponder is with find time diffrence of transmit and receive signal between transceiver station and transponder. This technique is called wity TDOA (Time Diffrence Of Arrival). After Distance between transceiver station and transponder is known, three-dimensional position can be searched with Trilateration methode;. This process will be simulated with software Maltab R2008a. KeywordsTDOA, Trilateration, ballistic rockets, transceiver, transponder