Abstract: Geometrical relationship between sensor vector and welding seam for welding mobile robot was investigated by applying least squares estimator method, then real-time identified algorithm of heading angle was proposed for welding mobile robot.Firstly, in order to accurately describe the space position relationship among welding torch, tracking sensor and welding seam deviation quantificationally, the concept of sensor vector was introduced.Then, according to the characteristics of sensor look-ahead, the position relationship between sensor vector and welding seam was fully described with once polynomial or quadratic polynomial in the little field of seam tracking.On the basis, real-time identified algorithm of heading angle was built based on the least squares estimator method.At last, the effectiveness of the proposed algorithm was verified by practical seam tracking experiment.As a result, it lay s the foundation for real-time seam tracking of complex curved welding seam for welding mobile robot.