Based on the analysis of the working principle, the general project and main functional module were presented for in process pneumatic measurement system of inner hole honing dimension. The influence of main parameters in each sector to the gauge during differential pneumatic measurement was analyzed, and the key module——pneumatic measurement module was designed and tested. The result showed that the design of in process pneumatic measurement system is feasible. It could bring a new method for the research on in process pneumatic measurement system for inner hole honing dimension. 