By analyzing the receiving signal strength and mobility of terminals in GEO satellite and terrestrial networks, a meth- od to estimate times of handover is derived. Then the number of handover signals, handover delay, signal quality and packet loss are used to form a model of handover cost. Based on the model, a handover strategy is proposed to choose different network to handover by different mobile terminals. Simulation results demonstrate that the strategy based on the model reduces handover times and delay in high speed terminal compared with the traditional methods.