The work aims to optimize the structure size of the wooden packaging box of a mechanical and electrical product for saving wood resources and reducing production cost of packaging boxes. The structure of the wooden pack-aging box was designed by UG according to the overall dimension, quality distribution and transportation requirements of the product. The 3D models of sleepers and longitudinal beams, which were the main load-bearing parts, were imported into Ansys Workbench. Then, the optimization models of sleepers and longitudinal beams were established for iterative analysis and solution to obtain the optimal solution of cross-section size, maximum deflection and volume of sleepers and longitudinal beams. Finally, the finite element analysis and comparison of sleepers and longitudinal beams were carried out before and after optimization. The optimal section width and height of the sleeper were 0.044 m and 0.032 m, and the optimal section width and height of the longitudinal beam were 0.148 m and 0.158 m under the condition of meeting the bending strength and rigidity. The total volume of the optimized sleepers and longitudinal beams were reduced by 41.324% and 8.661%, respectively, and the total mass of the packaging box was reduced by 34.79 kg, which realized the optimization goal of reducing wood consumption. Reasonable increase of cross-section height of sleepers and longitudi-nal beams can improve their rigidity, and the proper decrease of their cross-section width can significantly reduce their volume and mass.