Abstract: The space-time spectrum of target echoes are broadened and deformed in a shipborne high frequency radar via hybrid sky-surface wave propagation, which seriously affects the radar detection performance, due to the influence of the ionospheric random perturbation and the six degree of freedom motion of the receiving ship. This paper investigates the problem of modeling target echoes for this radar system. Firstly, the Doppler frequency shift characteristics of the target echo under dynamic spatial geometry are analyzed and the space-time target echo model under ideal conditions is established; On this basis, introducing the space-time phase perturbation effects of ionospheric irregularities and the six degree of freedom motion, the ionospheric random perturbation phase simulator and the six-dimensional oscillating perturbation phase model are constructed, respectively, and then the space-time target echo model of the shipborne high frequency radar via hybrid sky-surface wave propagation is established. Experimental data verify the effectiveness of the model.