At　present,　solar　cells　are　the　main　sources　for　spacecrafts.　For　a　long　time　the　bulk　of　the　space　power　installations　has　been　the　solar　arrays　based　on　single　junction　silicon　and　gallium　arsenide　solar　cells.　In　recent　years　a　trend　has　been　the　active　use　of　triple-junction　GaAs　solar　cell　with　higher　efficiency　instead　of　single　junction　solar　cells.　One　of　the　most　important　characteristics　of　solar　cells　used　in　spacecrafts　is　the　resistance　to　radiation　damages　caused　by　high　energy　particles　of　the　near-Earth　space.　According　to　the　spectral　response　of　triple-junction　GaAs　solar　cell　and　the　damage　characteristics　of　the　current　under　the　condition　of　electron　irradiation,　the　physical　mechanism　of　cell　attenuation　can　be　determined:　the　current　degradation　originates　mainly　from　the　GaInAs　subcells.　These　damages　form　additional　centers　of　nonradiative　recombination,　which　results　in　the　reduction　of　the　minority　charge　carrier　diffusion　lengths　and　in　degradation　of　the　solar　cells　photocurrent.　The　radiation　damage　caused　by　the　electron　irradiation　will　shorten　the　diffusion　length　of　the　base　region　and　affect　the　collection　of　photo　generated　carriers.　The　ways　of　improving　absorption　of　long　wavelength　light　in　GaInAs　subcells　with　a　thin　base　in　using　the　distributed　Bragg　reflector　can　be　investigated　by　the　mathematical　simulation　method　based　on　calculating　the　light　propagation　in　a　multilayer　structure　by　means　of　the　TFCalc　software　which　can　design　optical　structure.　To　estimate　the　validity　of　these　methods　for　solar　cells　structures　with　distributed　Bragg　reflector,　the　spectral　dependences　of　the　photoresponse　and　the　reflection　coefficient　with　different　base　thickness　values　are　calculated　and　compared　with　experimental　results.　Based　on　the　physical　mechanism　of　the　degradation,　the　thickness　of　middle　subcell　base　layer　is　reduced,　and　an　appropriate　structure　of　the　distributed　Bragg　reflector　is　simulated　by　the　TFCalc　software.　As　a　result,　the　new　structure　solar　cells　are　that　the　thickness　of　the　base　layer　is　1.5　mu　m　compared　with　the　different　middle　subcell　thickness　values,　and　the　distributed　Bragg　reflector　structure　with　15　paris　of　the　Al0.1Ga0.9As/Al0.9Ga0.1As　with　850　nm　central　wavelength　is　embedded　in　the　middle　subcell　of　the　base　layer,　the　distributed　Bragg　reflector　has　a　highest　reflectivity　of　more　than　97%　in　the　actual　test,　and　a　bandwidth　of　94　nm,　which　can　satisfy　design　requirement.　After　irradiating　the　new　structure　of　solar　cells,　the　decay　of　its　short-circuited　current　is　reduced　by　50%　compared　with　that　of　the　original　structure,　and　the　remaining　efficiency　factor　is　increased　by　2.3%.