In the last few years,along with GIS technology and Intemet technology unceasing development,WebGIS has widespread application.Because GIS has characteristic of quantity big data and rapid response and so on,classic WebGIS already could not well satisfy with browsing experience of user,like slow response of system,appearance "white screen" phenomenon and so on.Because Ajax engine selects asynchronous method to transmit the request of user,so it has solved structure problem of classic web application and improved user experience,it was applied in many web applications.Lightweight Ajax engine technology based on WebGIS has been studied under Ajax technology and the engine has been applied in WebGIS based on SVG vector map in paper.The goal is improve user experience and performance of classic WebGIS.Main research works in this paper are as follows:●Method for basic Ajax engine under.NET;●Method for lightweight Ajax engine;●Organization and coding scheme for geographic spatial data based on SVG;●Transformation method for geographic spatial data to SVG data.System model of WebGIS based on Ajax and SVG technology has been designed;system client's functions have been realized by SVG DOM technology and system server's functions have been realized by Oracle ODP.NET and Spatial technologies in this paper.It is shown that,compared with classic WebGIS,WebGIS based on Ajax and SVG technologies has many advantages as follows:●Refreshing map need not to load all pages and the operation is coherent.●System response is prompt and user's waiting time is short.●Some functions of server are transferred to client,thus loading balance between client and server is resolved.It can be believed that,WebGIS based on Ajax and SVG technology can give full advantages of both Ajax and SVG technologies,using Ajax to achieve refresh update map and using SVG to express no-zoom maps.It will improve user experience of WebGIS base on SVG map and it has the model significance to the WebGIS further development.