Grid systems at different levels have already been constructed around the world to provide users an easy way of accessing/integrating distributed computing, data and other resources. Portal layer is on the top of typical three layers in Grid system and provides presentation interface to the end-users. Portlets as executing components in portal layer usually access a specific Grid middleware rather than multi Grid middlewares. A new Grid system is implemented in this paper. It follows typical three layer structure of Grid system. By using UDDI registry, Grid Portlets in the portal layer can select services interfaces and find out suitable Grid middleware. Abstraction and Business Logics which are Java CoG-based in service layer will map to suitable Globus Toolkit middlewares. The endusers can use the Grid Portlets to access GT2, GT3 or GT4 middleware.