According to the deficiency of MapX point symbol library and analysis on MapX internal data structure and call mechanism of TrueType font symbol, a new extending method of TrueType font symbol in MapX is put forward by combining the structure of TrueType font file. The method can customize satisfactory TrueType font symbol base according to the specific needs of GIS application system. With the merits of simple, convenience and short development period, it can enriches the TrueType font symbol library of GIS application system based on MapX.