The space robot is an important tool for space on-orbit service. According to the requirement of the maintenance of the cooperative and non-cooperative targets, a multi-function on-orbit servicing robot system based on fastchangeable end-tools is proposed by investigating and analyzing the current research status of space robots, and a variety of end-effector design schemes are proposed. The three-finger-three-petal end-effector, as the quick-changing device for endeffectors and end tools, not only has the function of mechanical interface capture and docking, but also has the function of power/signal transmission and the mechanical power transmission function. The steel cable-snared end effector has superior misalignments tolerance and soft capture performance. It is suitable for capturing cooperative target with cooperative mechanical interface and non-cooperative engine nozzles of target satellite. The three-finger end-effector with underactuated mechanism has excellent capability of shape adaptation for the target and soft capture function, so it can be used to capture non-cooperative targets such as space garbage with irregular spatial shape. Through the research of the multi-function onorbit servicing robot system and the methods of end-effector quick changing, as well as the capture principles of the endeffectors, the multi-function on-orbit servicing robot system with fast-changeable end-effector and end tool has promising application prospects.