This paper investigates the trajectory optimization of pick-and-place for a cable-suspended modular parallel robot (CSMPR). A two-degree-of-freedom cable-suspended parallel robot, which includes two parallel cable spool modules, was designed, and its kinematic modeling was conducted. To enable the CSMPR to perform pick-and-place tasks in an environment with obstacles smoothly, this paper proposes a minimum snap trajectory optimization method based on a seventh-order polynomial trajectory, considering time allocation and corridor constraints. By defining a geometric corridor and selecting trajectory points to pass through within the corridor, obstacles can be effectively avoided, and the trajectory can be made smoother. By allocating time effectively, the peak values of speed and acceleration can be reduced, making the motion more stable. Through dynamic simulation, it has been verified that the optimized trajectory can avoid obstacles. Additionally, the change in rope tension for the optimized trajectory is much minor compared to the trajectory without time allocation during pick-and-place tasks, and the motion of the moving platform is smoother.