Abstract: The main factors that lead to the poor parallelism of the center line of the connecting rod large and small holes are obtained based on the process flow of the connecting rod of a reciprocating compressor. The finite element method is used to explore the optimal value of the clamping force of the fine boring process. Based on the mathematical statistics theory, the relationship between the drop of the positioning surface and the parallelism of the center line of the large and small holes in the fine boring process and the honing process has been experimentally studied. The results show that the optimal clamping force of the fine boring process is about 3.5 MPa. The positioning surface drop has a certain influence on the parallelism of the connecting rod size and hole in the fine boring process and the honing process, but the influence trend is not uniform, and the drop is 0 or close to 0, the parallelism of large and small holes is the best. The process improvement plan as follows. The clamping force of the fixture in the fine boring process is reduced from 4.5 MPa to 3.5 MPa. The fine boring process increases the positioning reference surface of the large end of the connecting rod by 25 μm, and the honing process increases the positioning reference surface of the small end of the connecting rod by 18μm. Use a floating honing fixture of the honing process . After continuous production verification for one year, the pass rate of parallelism of the center line of connecting rod large and small holes under the same production line process improvement program can be increased by about 1%.