The invention discloses a raster map building method based on local map splicing.The method comprises the following steps that 1, a robot scans and records environment information; 2, scanning data points are filtered to remove useless points; 3, local raster maps are calculated based on the filtered data through a ray tracking method; 4, sift feature points and corresponding feature descriptors of the local raster maps under two adjacent poses are calculated; 5, according to relevancy of the feature descriptors, the feature points are ranked, and feature points with small feather feature descriptors are filtered away; 6, the two local maps are subjected to iterative closest point algorithm ICP, and a transformation matrix of the two local maps is calculated; 7, the steps 1-6 are repeated, a transformation matrix of the whole path is recorded and completed, and finally data is merged to obtain a global raster map.The map is built through one-time laser data, so that the estimation error of the map is mainly the observation error of a laser sensor, and no estimation error exits.