Taking 3UPU parallel mechanism as the research object, the 3D model of the mechanism was established by using Solidwork software. The position and orientation characteristics, degree of freedom and coupling degree of the mechanism were analyzed according to the theory of position and orientation characteristics. The inverse kinematics solution of the mechanism was solved. A new numerical analysis method was used to analyze the workspace of the mechanism. The structural parameters of 3UPU parallel mechanism were optimized based on Fruit Fly Optimization Algorithm (FOA). The results show that the 3UPU parallel mechanism has a large workspace and the workspace has a void. The optimized parameters provide a basis for the prototype development and trajectory planning.