Abstract: The dynamic process of the weld pool is a high complex object with strong non linearity,mult variable coupling and a mount of stochastic and uncertain factors.It is very difficult to obtain an analysis mathematic model of weld pool dynamics.Thus the modeling of weld pool dynamics becomes a puzzle problem for weld technique engineers and control system designers,which also is an essence handicap in weld automation.In order to realize the effective control of the pulsed GTAW pool process,this paper investigated the dynamic characters of the pulsed GTAW from the classic control systems,and obtained two SISO transfer function models by the system identification method,one model for input pulsed time of welding current via output back weld width,the another for input weld travel speed via the output back weld width.The established models in this paper would be useful to study the controlled performance of weld pool dynamic process in the pulsed GTAW and can be used as has a valuable references and direction for designing its control system.