Abstract: When a large non-cooperative target is captured by a small space robot, the initial momentum of the target may be non-zero and unknown, and the disturbances to the base attitude are large, which will affect the real-time parametric identification of the on-orbit target. To solve this problem, the adaptive reaction null space control is used to minimize the disturbances to the base attitude. Moreover, a momentum increment equation containing the dynamic parameters of the target is established, which is used to compute the unknown parameters based on the angular/linear velocities of the base and angle/angular velocities of the manipulator joint obtained through on-orbit real-time measurements. The numerical simulation results show that the proposed algorithm is able to accurately identify the dynamic parameters of large non-cooperative target in real time when the initial momentum is non-zero and unknown, while maintaining the minimum disturbance to the base.