In order to resolve the problem of relative navigation during the course approaching a non-cooperative space target, a highly accurate state propagation model of non-cooperative relative orbit motion was proposed on the basis of the relative orbit dynamics equations and the second order Runge-Kutta formula. Taking the J₂ perturbation into account and expanding the target orbit equations into second order Taylor series beside the reference orbit, the angular velocity and the angular acceleration of reference orbit were further deduced and the relative orbit dynamics differential equation was built. After giving the initial value, the second order Runge-Kutta method was used to propagate the relative orbit motion. With the use of numerical integral method, the model can be widely used without any limited condition in relative orbit dynamics model forms; with the use of second order Runge-Kutta method, the computing efficiency is improved while the calculation accuracy is guaranteed. Two simulation scenarios, a low Earth orbit scenario and a high Earth orbit scenario, were designed to testify the generality and precision.