Abstract: Binocular vision technology which simulates the function of the human eyes to observe the world is used to compute the three-dimensional information of weld seam in the welding field;two cameras as binocular vision are fixed on the end effecter of the welding robot.The accuracy analysis model of vision computing is constructed.The effect of vision system structure on vision computing, and the effect of the position of weld seam and the relative pose of weld seam between vision sensors on accuracy are analyzed.An experiment base on model theory is designed to validate the model analysis results, which show the correctness of the constructed model.The effects of repeatability positioning accuracy and TCP calibration error of welding robot for visual computing are also analyzed and tested.The results show that the effect of the former factor is not bigger than 0.3 mm, but the re-calibration is necessary when the calibrated error of TCP is bigger than 1 mm.