Adiode-pumpedmasteroscillatorpoweramplifiersystembasedonacryogenicYb:YAGactive-mirrorlaserhasbeendeveloped.Theperformancesofthelaseramplifieratlowtemperatureandroomtemperaturehavebeeninvestigatedtheoreticallyandexperimentally.Amaximumoutputenergyof3.05Jwithanoptical-to-opticalefficiencyof14.7%hasbeenachievedbyusingthemasteramplifiersystem.