The invention belongs to the technical field of automatic control, and provides a topmark map building and robot positioning method. The topmark map building and robot positioning method comprises thesteps: S1, whether a positioning mode is entered currently or not is judged, if yes, the positioning mode is entered, the step S2, the step S3 and the step S4 are executed, and if not, a mapping modeis entered, and the step S2 to the step S6 are executed; S2, topmarks in a current map are extracted, ID of the topmarks is obtained, and the positions of the topmarks in the map are calculated; S3,the known and unknown topmarks in the current map are extracted; S4, the pose of a robot in the current road sign map is calculated based on the three or more known topmarks; S5, a transition matrix R' and a translation vector t' from a topmark coordinate system to a map coordinate system are calculated; and S6, coordinates x<w> of the unknown topmarks in the road sign map are calculated based oncoordinates x<map> of the unknown topmarks in the topmark coordinate system, and the road sign map is updated. Positions of the unknown topmarks in the road sign map are calculated based on the transition matrix and the translation vector from the current topmark coordinate system to the map coordinate system, that is, the road sign map is built, and accumulation of errors can be weakened.