Abstract: Similar to rocket vehicle,space vehicle can be divided intosingle and multistage ones.A multistage space vehicle consists of several spacevehicles with engines(by series-mounting).This paper deals with the opti-mal orbital transfer for this class of space vehicle.The optimal orbital transfer of a thrust-limited multistage space vehiclebelongs essentially to a multistage optimal control problem.Using the solvingprinciple of a multistage optimal control problem,this paper discusses twokinds of the problems of the optimal transfer between two circular coplanerorbits for a thrust-limited two-stage space vehicle,gives the solving equationsand conditions of determining optimum thrust programs and optimum trans-fer orbit for the two kinds of problems.Especially,the conditions to besatisfied at the stage-to-stage separation moment are examined.The concept introduced in this paper is adaptable to the problems of opti-mal transfer between non-circular and non-coplaner orbits.