In response to the traditional RRT algorithm in the complex environment, the mobile robotic arm avoidance planning is low, and the current work demand problem cannot be met, an improved RRT avoidance path algorithm is proposed. By introducing an obstacle factor, the number of samples is reduced, by constraining the new node generation mode, the growth direction of the new node is always toward the target point, which speeds up the search speed. Adopting a gentle-step strategy, effectively avoiding oscillating phenomena near the target point. The planned path is smoothed by simplifying the path and combining with local cubic B-spline curve, the length of the path is shortened, and the stability of the robot arm is improved. MATLAB simulation results show that the average path length of the improved RRT algorithm is shortened by 20%, the average number of sampling points is reduced by 62%, and the number of turning points is reduced by 96%. The convergence speed is fast and the time is optimal, which can meet the obstacle avoidance path planning of the mobile manipulator in special environment, and has good feasibility and effectiveness.