Abstract: Container NC welding machine includes multi-sensor system, computer control system and step motor drive system. Data process in multi-sensor is the key part of this mechine.Container floor and the sidewall weld is broken line.For the weld is 12 meters long, and allowance exits in machine and fix, and welding induces deformation, therefore automatic welding must take action of the seam track.The multi-sensor system consists of laser sensor and high-precision ultrasonic sensor, for straight bead ultrasonic sensor controls the distance from welding torch to side wall.While for the turn corner bead the system uses expert system for data fusion of two sensor signals and a find decision is made.Torch position can be adjusted in order to weld continuously.It can also provide a theoretical foundation for the various curves seam tracking study in the future.