Abstract: Aiming at the technical problem that it is difficult to extract the weld position information under the manifold of cylinder wall with different diameters on the workpiece, a weld position recognition sensor that can identify the spatial position and size information of the branch pipe is designed. The data collected by the device is combined with known the spatial position and size information of the workpiece, establish the position model of the pipe insertion weld, and derive the weld feature matrix and welding torch attitude matrix based on this model. The collected data is combined with the above mathematical model and simulated in MATLAB for comparison.The test results show that the maximum accuracy error is 0.25 mm, which meets the actual welding accuracy requirements, and verifies the accuracy of the sensor and the mathematical model. The sensor and its weld feature recognition method are universal and have important significance for the automation and intelligence of pipe plug welding tasks.