To ensure the safe and precise collaboration between humanoid robotic arms and astronauts in the lunar environment， this paper investigates a six-degree-of-freedom （6-DOF） humanoid arm and proposes a dynamic parameter identification method based on its dynamic characteristics. First， the kinematic and dynamic models of the humanoid arm are established. For the extremely low-speed collaborative scenarios， the dynamic model is simplified to obtain the minimal set of composite gravitational parameters and its corresponding gravity regressor matrix. Second， the trajectory optimization objective is set to maximize the feasible parameter space of the gravity regression matrix， with constraints incorporating the humanoid arm’s motion limits and collision avoidance. Finally， simulations and experiments are conducted in both a simulated lunar gravity environment and an earth gravity environment. The results show that the average percentage error of the calculated joint torques after identification is only 5.5% in the lunar simulation and the mean absolute error of the joint torques is significantly smaller than the average noise amplitude in the experimental validation. Results demonstrate that the dynamic model established by the proposed identification method can accurately reflect the dynamic characteristics of the humanoid arm during extremely low-speed motion.