It is well known that the use of aeroassisted orbital transfer can save fuel efficiently, thus representing one of development trends of new orbital transfer technology. This paper is concerned with the problem of coplanar orbital transfer of spacecraft from high earth orbit to low earth orbit based on Gauss pseudospectral method (GPM). With the consideration of heating rate limit and control constraints, sub-optimal trajectory of spacecraft’s flight in atmosphere was obtained. On the analysis of trajectory characteristic the first-order necessary optimality conditions of optimized results was demonstrated. Indirect method was also adopted to solve the problem, then the calculation results of the two methods were compared. Simulation results show that it is a simple way to handle constraints with GPM, and it has high precision solutions and can overcome the disadvantages of the indirect method, such as initial value sensitivity and poor robustness. Therefore, GPM is suitable to be applied in the problem of atmospheric spacecraft trajectory optimization.