In view of human exploration of Mars, the three-degree-of-freedom dynamic model of aerocapture trajectory was established. The constraints which satisfy the mission requirements were listed, and the entry corridor was obtained. The influence of some parameters on the trajectory shape was analyzed. A pipelining optimization approach of Genetic Algorithm(GA) and Sequential Quadratic Programming(SQP) were introduced to analyze the attainable region of flight through bank angle control. The results indicate that, compared with direct deceleration by retro-rocket, aerocapture mode is highly advantageous in energy requirement, and has good maneuver ability. It is a feasible approach for manned spacecraft to insert into Mars orbit.