We carried out simultaneous surveys of 22 GHz H2O and 44 and 95 GHz class I CH3OH masers toward about 500 high-mass YSOs in a wide range of evolutionary phases using the Korean VLBI Network (KVN) 21-m telescopes. The sources are infrared dark cloud cores, high-mass protostellar objects, 6.7 GHz class II CH3OH maser sources, ultracompact HII regions. In this presentation, we will report the main results of our maser survey.