The two-stage solid ascent vehicle is an important part of the large-scale Mars sample recovery program. To address the problems of the optimal thrust design and the depleted shutdown guidance with multi-constraints for solid Mars ascent vehicles in sample return missions， an analytical-numerical fusion method for optimization of the orbit entry phase is proposed， in which the analytical optimization method provides the theoretical basis for the optimal design of the solid thrust， and the numerical optimization method further solves the problem of depleted shutdown guidance faced in the actual flight in the proximity of the theoretically optimal solution. Firstly， to analyze and optimize the thrust parameters of the solid ascent vehicles under the maximum load mass， the problem of optimal control of the thrust direction is constructed based on the Pontryagin maximum principle. A new necessary condition of the optimal thrust parameters is derived to eliminate the costate multiplier vector， so that the analytical expression of the optimal control commands is obtained. Secondly， considering the parameter deviation and uncertainty interference of the ascent vehicles under actual flight conditions， a quadratic numerical optimization method combining the optimal analytical solution sequence is proposed to guide the Mars ascent vehicle to the predetermined target orbit with high accuracy in the depleted shutdown mode， which can quickly calculate the flight commands online by the efficient inverse recursive sensitivity matrix. Finally， a comparison with the GPOPS optimization method verifies the optimality and correctness of the proposed analytical expression. The optimal thrust scheme of Mars ascent vehicles is also given. The numerical simulation results demonstrate that the Mars ascent vehicle can enter the target orbit with high accuracy in the depleted shutdown mode with the interference of deviation and uncertainties by the proposed method.