In order to realize the hghprecision positioning and map construction for unmanned combat platforms in complex environments, we proposed a precision positioning and mapping method based on monocular visual SLAM with WLAN adided. This method can estimate the scale factor of monocular VSLAM and get the position in real scale space. Furthermore, the result of the WLAN location and the monocular vision positioning is fused by the factor graph model, realizing accurate positioning and sparse mapping. The experiment shows that this method can estimate scale factor well and reach the positioning accuracy of decimeter, and has important engineering and practical significance in applications such as unmanned reconnaissance, search and resue in complex environments.