Abstract： It is difficult to control the position of the torch very accurately for long periods because of the errors caused by the processing of pipeline and orbital assembled and thermal deformation. To adjust the torch height at a constant length is one of the key factors to guarantee the welding quality in the allposition of pipeline welding. A mathematical model was built regarding the relationship between the welding current and the CTWD, a multimodel variablegain PID control algorithm was proposed, and a multi-model controller based on fuzzy switching rules was designed to deal with the changes of welding standard in allposition welding. The test results show a good steady state and dynamic performance in CTWD control. The realtime CTWD control in different welding standard can be achieved. These methods ensure the stability of the welding process and improve the quality of welding.