Bitmap fonts are used to display in VxWorks5.5, which is simple and widely used. But it will not meet the demand when we don't make sure which font size is ok as each bitmap font file has only one font and one size. We can achieve a variety of fonts and sizes by using the TrueType fonts and FreeType font engine. This paper describes the basic principle of TrueType and FreeType technology, and how to realize outline font display by using WindML, FreeType and TrueType fonts .