Aiming at the trajectory prediction in forecast handover process of early warning detection system, a method of prediction trajectory for unpowered gliding hypersonic vehicle in the gliding phase is proposed. Firstly, the motion characteristic of the unpowered glide hypersonic vehicle in gliding phase is analyzed to verify the feasibility of using a polynomial model to predict the target trajectory. Then introduces the trajectory prediction principle based on polynomial model and the data processing techniques, segmentation method and midpoint smoothing method, to reduce impact of the state estimation error to the trajectory prediction accuracy. Finally, the optimal parameters of the polynomial model are obtained and the validity of trajectory prediction method is verified by simulation.