Abstract: Sincethethrustamplitudeofthemainengineonspacecraftisunadjustable，amultipleterminalconstrainbasedoptimalguidancemethodwasproposed，consideringthedeficiencyofsmallcorrectionangleassumptionofconventionaliterativeguidanceunderfiveterminalconstrains.Anoptimalcontrolmodelwasestablishedintheorbitinjectionorbitalcoordinateframe.Transversalityequationswaredirectlysolvedbyiterationtoobtaintheguidanceanglecommand.Theswitchonandoffinstantswerethenoptimizedtoreducetheinfluenceofunsatisfiedterminalconstraints.Besides, thefiveequivalentterminalconstraintsinthegeocentricinertialcoordinateframewerederivedandappropriateweightfactorswereadjustedtoimprovetheprecisionofnumericalsolvingofguidanceequations.Simulationsonstandardconditionsdemonstratethattheproposedguidancemethodhasincreasedtheprecisionofunsatisfiedterminalconstraintsby1595355m，comparedwiththeconventionaliterativeguidance.TheMonteCarlosimulationsshowtheadaptabilityoftheproposedmethodtotheinitialbiasofthespacecraftpositionandvelocity.

Key words: spacecraftorbittransfer, iterativeguidance, optimalcontrol, coordinatetransformation, switchonandoffinstantsoptimization, weightadjustment