To solve the problem of local map building in the field of mobile robot navigation, we analyze advantages and drawbacks of several kinds of range finders, the model of laser range finder and its nonlinear problem which appears in local map building. A novel method is presented based on commonly model in autonomous mobile robot local map building. This method adopts weighted least means square to build local map and it can be easily implemented and has high precision. The emulation and experiment result shows that the method can effectively reduce the error of curve fitting in the field of robot navigation.