Space robot's capturing non-cooperative unknown target will change the system＇s dynamics parameters , reduce the precision and accuracy of the system path planning and control. Therefore, orbiting parameters identification of unknown target is necessary for motion control in space robot. Based on the conservation principle of linear and angular momentum, the existing-identification methods, which consider target as one part of the the end-point and end-effectors of the space robot, are dynamics parameters of the end-point and end-effectors but not the dynamics parameters identification of the unknown target. Besides, they need to measure a variety of sensor information to identify the object parameters. A new method is proposed based on D＇Alembert principle and Euler equation in an inertial frame of reference, which could identify dynamics parameters of unknown with measurement of force and moment exerted on the end-point of the robot through the six-dimensional wrist force sensor. To show the validity of the proposed scheme, an experiment is conducted by using an equivalent-weightlessness model to remove the effects of the gravity of space robot and object, with the IRB 120 robot produced by ABB Company. The resuhs show that the method can gain high identification precision and is suitable for practical engineering application.