Abstract: GOCE is the first satellite in theworld using air drag compensation technology for scientificmeasurement mission，to bemore specific is for Gravity field and steady-state Ocean Circulation Explorerm ission.The British T5 ion thruster is the key unit in air drag com pensation system.Thanks to its excellent performance，it flaw lessly carried out the mission.It depicts the technical characteristics，working conditions and performance of T5 ion thruster from very beginning of orbit insertation until the end of themission，and summarizes theapplication of T5 ion thruster in air darg compensation system，eventually proposing suggestions for the developementand applicationsof air drag compensation system.