The challenge of achieving compliant assembly of electrical connectors by robots in space environment is a major technical issue. This paper starts from the basic principle of peg-hole assembly with clearance fit, and proposes a task priority control strategy based on force/torque inequality constraints. A contact search task control model for peg-hole assembly with force-inspired is constructed. The end-effector adaptive compliant control of the robot is used to realize the transformation of contact search from non-contact to side contact, from end face dual-point contact to end face alignment. The peg-hole assembly and electrical connector assembly experiments are conducted. Among them, the autonomous compliant assembly of an electrical connector used in-orbit by robot is conducted with 41 ground experiments, the success rate of assembly task is above 93%, the average successful assembly time is 101 s, which verifies the effectiveness of the control strategy and assembly method, laying a theoretical and technical foundation for the fine operation of space robots.