The statistics of Korean Maritime Safety Tribunal and Japan Marine Accidents Inquiry Agency shows that the major muses of collision at sea are Improper lookout and Non-compliance with marine traffic rules. Those two muses are occupying more than 70% of collision, and it's clear that those muses are undoubtedly closely related to simple human error. In this paper we tried to find out the root muses of this kind of human error of OOWs(officers on watch) through risk identification method and studied how to tackle them via risk control theory. In conclusion, the measures studied in this paper could be applied to help OOWs avoid their own human error as well as be used in shipping company for their fleets' safety management.