A method based on linear matrix inequalities (LMI) constraints was presented for the re-entry longitudinal guidance law with intricate constraints. The nonlinear longitudinal dynamic equations were modeled pseudo-linearly for controllability in the standard trajectory neighborhood area,and then the guidance law was designed by solving LMI convex optimal. In each control period the feedback control law and input were obtained. The control input was used to guide the actual reentry trajectory, and closed-loop systems stability was proved. Simulation results show that the proposed guidance law is robust to deviations from reentry initial states.