The development of geospatial web service has revolutionized how geographic data is used today and offered brand new possibilities for innovated applications. One noteworthy evolution is the easier making of customized maps that meets particular domain needs. To take full advantage of the abundant and distributed geospatial web service as the source of map contents, we proposed a middleware prototype to aid customized maps making in this paper. The adoption of geospatial web service complying with the OGC standards not only simplifies the accessibility of geographic data, but also improves its interoperability at clients' environment. As the number of internet-based georesource continues to grow in the future, the proposed prototype can be practically applied to create new applications and brings positive impact to the future GIS environment.