Abstract: The vectorization of mining engineering drawing is to convert the raster bitmap obtained by scanning the mining engineering drawing to vector diagram for CAD system.The paper puts forward a noise filtering method while maintaining the detail information based on characteristics of engineering drawing and designs a simple character filter for the filtering of character of different strikes based on the mathematic morphology theory.The paper uses Freeman and Hiditch method to construct link code and obtain line thinning.The paper also puts forward a new method to preselect the key points to fit the curve by the help of genetic algorithm meethod.