Abstract: Owing to the limitations of RGB-D sensor， there will be some situations where the depth information does not exist or is incomplete in the practical application， which will affect the accuracy of RGB-D SLAM system that mostly depends on the depth information.An RGB-D SLAM optimization method is proposed to fuse monocular information.Through the analysis of depth image， three judging conditions are put forward respectively from the existence， accuracy and discreteness of depth information， which can be used as the basis of the selection of monocular or RGB-D processing mode.This new system makes the SLAM system with RGB-D camera more accurate and robust.Finally， the system is compared with other SLAM systems by running data sets， and the experimental results verify its feasibility.

Key words: RGB-D SLAM, monocular information, fusion, judgment mechanism, optimization