In this study, we present a sequential convex programming method for the reentry trajectory optimization problem with a piecewise constant bank angle profile constraint. Firstly, we design a piecewise constant bank angle profile that includes two free-time nodes to reserve maneuverability. Then, to handle the nondifferentiability of the profile at the piecewise points, the reentry problem is reformulated in a multiphase form so that the profile is differentiable in each phase. Finally, we convert the nonlinear multiphase problem into a sequence of convex subproblems by successive convexification. By iteratively solving these subproblems, a feasible solution to the original problem can be obtained. Numerical simulations demonstrate the effectiveness of our proposed method in short, medium, and long downrange reentry scenarios.