Aiming at the urgent problem existed in today's constructions of marine information system that the marine spatial data cannot be sweepingly accessed and shared by ordinary people, this paper proposes a Web System for Marine Spatial Information Service based on Electronic Nautical Charts. However, the Electronic Nautical Charts System has its own complicated nautical symbol that is different from the common GIS platform. So the web service of Electronic Nautical Chart (ENC) data conformed to Vector Chart Format (VCF) is not completely supported by ArcIMS which is a Web-GIS platform for land-use produced by USA Environmental System Research Institute (ESRI) Company. This paper presents a novel method that ArcIMS's symbol libraries extension is used to fulfill the specialized chart visualization by using the COM-based GIS component MapObjects. This system accepts ENC data coded in Chinese VCF, and develops COM-based nautical symbol library software for nautical chart mapping, and then adopts MapObjects to extend ArcIMSs symbol libraries, and last distributes ENC service by ArcIMS and ArcSDE. Unlike previous works, the method presented by this paper decreases the difficulty of software development and shortens the period of software development. Furthermore, the COM-based framework makes it convenient to extend system function flexible by developing new specific models as a component. To validate the feasibility of proposed system, authors implement a prototype system.