Abstract: To address the low efficiency and poor smoothness of material handling with SCARA robots, a staged cooperative trajectory planning method is proposed. Considering the functional differences of each joint during handling, a 4-5-4 segmented polynomial trajectory is designed for the first and second joints to achieve smooth transitions in planar motion, while a fifth-order polynomial trajectory is applied to the third and fourth joints to ensure continuity and smoothness in vertical grasping and end-effector orientation adjustment. By coordinating the staged motion of all joints, the complete material handling trajectory is realized. To further enhance efficiency, a firework particle swarm optimization (FW-PSO) algorithm is employed to optimize the 4-5-4 segmented polynomial trajectory for time-optimal performance. Simulation results demonstrate that, compared with the traditional PSO and adaptive IPSO (improved particle swarm optimization) algorithms, the FW-PSO reduces the execution time of the segmented trajectory by approximately 11.3% and 7.4%, respectively, thereby significantly improving handling efficiency. Moreover, the proposed trajectory ensures that joint displacement, velocity, and acceleration remain smooth and free of abrupt changes throughout execution, thus guaranteeing stable robotic motion.