Freshwater fish head before processing as a freshwater fish processing a difficult point in the process of automated processing, to head the processing effect directly affects and restricts the freshwater fish late deep processing of the quality of the products. This paper presents A use of pneumatic cylinders contour design tool for freshwater fish mechanical processing way to head, is designed and developed A pneumatic head machine prototype, to go head machine prototype meat rate and recovery rate of head as the main performance indexes, performance parameters affecting the freshwater fish head machine prototype of fish head positioning distance, the back of the fish body position distance, tool shape structure, the working pressure, etc. The key factor to determine the test index and orthogonal experiment design and analysis, it is concluded that: to go head to head machine effect from large to small in the order: A fish head positioning distance ＞ C cutter contour structure ＞ B ＞ fish back positioning distance D error. Comprehensive evaluation of the results of the analysis shows that: freshwater fish go pneumatic head machine head work, put the fish body horizontal, fish head positioning distance is 107 mm, the back of the fish body positioning distance is 55 mm, and the thickness of 2 mm of u-shaped arc blade knife cutting head effect is best, at this time the fish head meat at a rate of 76.8%, to head a rate of 90.6%.