In order to assess the accuracy of camera calibration results accurately, based on the evaluation method of the length of the chessboard grid, a method for evaluating the accuracy of camera calibration based on external parameters was proposed. The same group of images was calibrated twice by this method to obtain the world coordinate system in two different positions. The distance of origins of two world coordinate system were found by using the calibration results, and was compared with the actual distance. The accuracy of external parameters in calibration resules is described quite visually, and then the accuracy of camera calibration results is further evaluated.