In order to maximize the range of reentry, the trajectory of hypersonic glide-reentry vehicle is studied. The optimal trajectory is obtained using legendre pseudospactral method (LPM). The effect of the path constraints on the trajectory is analyzed. Furthermore, the regulation of the control variable of the constrained trajectory is analyzed. According to the rule, a piecewise linear model of the coefficient of lift is proposed. Numerical simulation shows that the trajectory derived by this model is very similar to the optimal trajectory, and the ranges of the two trajectories are nearly the same, demonstrating a good control method for the maximum-range trajectory.