Aiming at the problem that the output displacement of the piezoelectric actuator is small and the coupling motion of the positioning platform affects the positioning accuracy, we designed a 2-DOF decoupling large-stroke precision positioning platform. First, a dynamic model based on the lumped mass method was established and verified by simulation. The multi-objective genetic optimization algorithm was used to optimize the structural size parameters of the positioning platform, and the optimal solution set of the structural size parameters of the positioning platform was obtained. Finally, according to the theoretical and simulation results, a prototype was fabricated and the working stroke, decoupling performance and natural frequency were tested experimentally. The results show the coupling rates between axes of the positioning platform in the x-direction and y-direction are 1.31 % and 1.62 %, respectively, the natural frequency is 337.2 Hz, and the positioning stroke is 89.2 μm×85.9 μm. The positioning platform designed in this paper is decoupled and has a large output stroke.