The equilibrium condition of hypersonic vehicle during cruise phase is modeled, under which the vehicle can maintain constant speed and altitude. It analyzed the equilibrium conditions that the vehicle can satisfy. Based on the conditions, a guidance law with multiple constraints and terminal course angular constraint is proposed, and the analytic solution is concluded. The method is adaptive since the guidance command is obtained through the analytic expressions in real time. In the end, simulations under different deviations have proved the method is effective.