Abstract: A pipeline flash butt on-line monitoring system is established, and the real-time data acquisition, on-line monitoring and high speed data storage of the pipeline process parameters such as flash butt welding voltage, welding current, displacement and pressure are realized by the system. For X65 pipeline flash butt welding,tests are designed by orthogonal experiment. Based on the tests results and those welding parameters data recorded by the pipeline flash butt on-line monitoring system, welding parameters are optimized. The changes of welding current and welding rate are investigated by comparative analysis of the mean and standard deviation of welding current at different welding stages of each test in order to provide basis for welding parameters nonlinear adaptive controlling.