Abstract: GML is a markup language based on XML.But it is not designed to be a web-map publishing format that can be displayed in web browser.With the help of XSLT language, GML files can be transformed to SVG files for deeper interaction with users and better visualization effect.And Traditional XSLT processors usually use DOM skill to parse GML files, which does not play well on large GML files with mass data.This paper provides a method that supports the transformation from large GML to SVG, and we have developed a optimized XSLT processor, GSxslt, based on the method.The algorithm takes SAX parsing skill instead of DOM one.Meanwhile it has optimized XSL files that are needed in the process of transformation.It implements an optimized algorithm, which is designed to classify the XSL file for higher efficiency.Experiments show that GSxslt do have a better performance, compared with the traditional ones.