Map building in unknown environment maps is the key to mobile robot navigation. This paper studied the method of building indoor map, discussed the way of extracting the feature of indoor environment, as well as described the main problems of map building and solutions to them. To get the indoor map, we used LMS100 laser sensor of SICK to get the envrionment information, extracted environmental characteristics and matched local map and global map. By getting envrionment information, it is solve the problem of uncertainty error from odometry to robot. Then experiments are given to show reliability and practicality of the method.