The finite element modal analysis of the frame was performed in designing the frame of doublesided orchard ditching machine. Its first 6order frequency and mode shape was obtained and structural performance was analyzed to deal with strength and stiffness issues of frames after importing into ANSYS Workbench whose parametric solid modeling of fixed and folded frames established by Creo. Results showed that the vibration of the fixed section frame was large. It was easy to cause stress concentration and fatigue cracking or even fracture. An improved solution for the frame structure for the fixed section frame was proposed to increase the reliability by adding trusses and eliminating welding residual stress while using structural strength and stiffness as the optimization target with loworder modal frequencies and vibration amplitude as reference standards. The results showed that the first 6order natural frequency of the improved fixed section ranged from 52.884 to 135.77 Hz. The maximum deformation was 0.055 724 mm. The loworder modal frequency and vibration amplitude were effectively improved. The rigidity has been greatly improved to meet requirements of design. The result of modal test showed that the maximum error percentage of the natural frequency of the finite element modal analysis and the modal test results was 0.857%. The vibration mode was basically same. Field validation indicated that the application of the improved frame proved that work quality was in full compliance with the NY/T 740―2003 operation quality standards. The performance was stable,meeting the horticultural requirements of the orchard ditching machine. The combination of finite element modal analysis and structural performance analysis can reduce the customization steps of the initial design,shortening the cycle of mechanical design. It will provide a reference for its practical applications.