The rotor suspended spray bar combines the advantages of ground machinery and aerial UAV respectively, which can simplify the complex truss structure and reduce the secondary pollution caused by droplet drift through the rotor downwind field. It has a good application prospect. It is difficult to retract the rotor suspended spray bar in the traditional retraction and retraction mode. Therefore, an automatic boom retraction and retraction device with a regular quadrilateral cylinder as the main body was proposed, the D-H coordinate system and the forward kinematics model of the boom retraction and retraction process were established, the dynamics model was constructed by Newton Euler method, and the optimal trajectory of the boom retraction and retraction was obtained by using cubic uniform B-spline curve trajectory planning. Taking the movement time, joint impact and energy consumption of the boom retraction and retraction as the multi-objective function, the Pareto solution set was solved by NSGA-Ⅱ algorithm. The boom retraction and retraction test was conducted by selecting the trajectory of the boom deployment time in the solution set as 56s, 61s, 66s, 71s, 76s and 81s, and the boom retraction time as 54s, 59s, 64s, 69s, 74s and 79s. The test results showed that there was a significant relationship between the movement time of the spray bar and the standard deviation of the spray bar angle. The shorter the movement time was, the worse the stability of the spray bar was, the greater the joint impact was, and the more energy consumption was. When the trajectory corresponding to the boom retraction time of 59s, 61s was taken as the optimal trajectory for boom retraction and retraction, the average tracking error between the drum speed and the planned speed was no more than 0.201(°)/s, and the average tracking error between the actual motion angle and the planned angle of joints 3, 4, and 5 was no more than 6.201°. The boom can better track the optimal trajectory to complete retraction and retraction. The research verified the effectiveness of the automatic boom retraction and retraction device and the accuracy of the optimal trajectory of boom retraction and retraction.