Abstract: Based on the analysis of practical workpiece position calibration,an algorithm for calibrating workpiece position based on simulated annealing was carried out for robot welding.By teaching 3 or more points that were far away from each other and not collinear as possible with the real robot,the position information was obtained implicitly.Then a simulated annealing algorithm was designed for calculating the transform matrix from the model to the real workpiece.It was a universal and precise algorithm.The max calculation error is under 0.02 mm max.To a certain extend,teaching error may affect the calibration result.Generally,the calibration error is under 0.5 mm,and under 0.9 mm in the extreme.If the calibration was performed before path planning,the program generated off-line could be downloaded directly to the robot controller.