This paper describes a phase sensitive optical time-domain reflectometer(φ-OTDR utilizes optical fibers to achieve distributed measurement of vibrations along the route,φ-OTDR reflects the vibration state along the fiber optic line through optical phase changes,and phase extraction is φ-The key to OTDR technology.It introduces the implementation method of program design and provides a flowchart for the main steps of digital orthogonal demodulation,vibration positioning,and phase unwrapping in the phase extraction process.Verify the effectiveness of the implementation method through data processing.