In order to develop an open source and cross-platform application to replace costly commercial WebGIS softwares for Web electronic chart service, the paper, based on MapServer and its heart Mapfile, studied the key technologies for data access and cartographic expression of electronic chart data. The research opened up a new way for researching Web electronic chart service, and it would help to reach a low-cost solution for Web electronic chart service and accelerate its popularization in the shipping information field.