Conducted is theoretical calculation to explore mutual interference of the main frame with the sub-frame and proved are bend and mismatch of the frame and sub-frame before the interference occurs. Applied is the ANSYS Workbench to conduct analog simulation for testing and verifying the validity of the theoretical analysis， it is pointed out that the interference of the sub-frame to the main frame flange far away from the gusset plate is serious and further proposed is a solution for realizing the frame and sub-frame rigidness matching， that is， thickness of the sub-frame is increased from5 mmof7.2 mm. Applied is the “Concentration Contact Method” to analyze， test and verify the feasibility of the solution and the analysis results show that deformation of key points in the main frame is decreased by more than 10 %， mutual interference of the main frame with the sub-frame is reduced significantly and the reduction is more than 40 %.