The invention of medical-used linear accelerator (Linac) in 1950’s and its rapid developement over the past four decades have significantly changed the outlook of radiation therapy in cancer treatment. Medical-used Linac is a sophisticated medical device which integrates delicate electronic and mechanical parts. In order to normally operate with high accuracy, maintenance on a routine basis is esstential. This article briefly reviews the milestones of Linac developement chronologically. This article also outlines the recommended maintenance programs currently applied at this department that maybe useful for users.