Abstract: Flaring connection is the most widely used type of connection for aircraft at present, and its manufacturing accuracy directly affects the sealing performance of aircraft pipeline. Aiming at the problems of poor precision, surface defects and low production efficiency caused by the heavy reliance on special tooling and manual operation in the production process of the traditional aircraft flared duct, in this paper, the digital measurement technology is integrated into the two main processes of pipe cutting and expanding, and the closed loop of manufacturing process is formed by data acquisition and feedback, thus the manufacturing precision of expanding pipe is optimized. This paper first introduces the overall structure of aircraft duct closed-loop fabrication, and then analyzes the closed-loop control of two main processes of duct allowance cutting and duct expanding, and gives the main calculation model and system composition. Finally, an aircraft duct is taken as an example to verify the correctness and practicability of the method and the calculation model.