Abstract: Taking the main structure of a lightweight non-contact gantry laser processing machine as the research object, the finite element model of the mechanism was established on the ANSYS platform using the finite element analysis method, and based on model analysis theory, solving the structure of the first six order natural frequency and vibration mode, its stiffness distribution characteristics and structural design rationality were analyzed. Further through the modal superposition method, the displacement response characteristics of the maximum deformation point and the actual concern point are obtained, and the two sensitive frequencies that the main structure should avoid are found: 48.63 Hz and 55.31 Hz, which provide a theoretical reference for the dynamic design and optimization of lightweight gantry laser processing machine.