Abstract: According to stagger problem of problem plate butt welding, this paper proposed a method with composite bridge by combining the capacitance and inductance for weld automatic tracking, and designed the structure of sensor. With sensitive detection of the plate spacing change by capacitance and of the edge change by inductance, this composite bridge seam tracking sensor can determine the relationship between horizontal and vertical position of the welding torch. This method is of non-contact, high sensitivity, strong anti-jamming capability, fast response speed and reliable operation, and can solve the misalignment problem during plate butt welding to a certain extent. Seam tracking experiments results made on a simple platform show that the effect was good and it provided a new method for seam automatic tracking technology.