In order to investigate the influence of camera inner parameters to the measuring precision, the camera inner parameters such as focal length, imaging center and distortion coefficient were taken as input variables of the Monte Carlo Method (MCM), and success rates of pose determination was used to measure the influence degree of each input variable to the measuring precision.Statistics was made through simulation for the pose measuring errors caused by the same input error in multiple image surfaces.The simulation result shows that:1) The impact of focus error on measuring precision increases as the imaging point of target feature deviates from the imaging center;2) The impact of the imaging center error on the measuring precision has no obvious change in the whole image surface;and 3) The error of pose measuring increases with the distortion of image regions.Therefore, improving the precision of focal length and distortion coefficient would increase the pose measuring precision of outer imaging regions, while the measuring precision in the entire imaging surface region would be increased by decreasing the imaging center error.