This paper discusses the defects of the traditional way of map printing quality detection, which is not adapted to digital and standardization demand of map printing. With the analysis of the element characteristics of the linear map, the theory model of the linear map printing quality auto detection system, based on dynamic threshold algorithm, is put forward. And the way of making the standard map image, image registration and the printing defects extraction is studied in the paper. The experiment shows that this algorithm has high detection precision, and can avoid the interferential pixel which may affect the judgment of printing defects. At the same time, the feasibility of this scheme is available and it has important significance for the improvement of linear map printing speed.