Abstract: The calibration method of TCF and base frame of dual-robot were studied based on the task of dual-robot coordinate welding. A calibration algorithm was proposed by using quaternion to represent the coordinates of the position and orientation, so was the base calibration system calibration project of dual-robot on the basis of the method of"three point and two-steps based on the public target". The TCF calibration calculation was simplified because of the transformational relation between rotation matrix and quaternion which was inferred according to the theory of vector rotation. Two initial rotation matrix differential value of F-norm obtained by calibration was served as optimized objective function, the precise value of calibration was obtained by using Lagrange multiplier method. At last, the tests of TCF and dual-robot calibration were implemented by the calibration strategy mentioned above. Experimental results showed that the accuracy of calibration was improved and the error of calibration was decreased effectively.