The problems of marine spatial planning relate to the difficulties and time consuming in using any scenarios for sustainable development by using traditional spatial planning method, either manually or digitally. Geographical information system (GIS) software is able to develop a model of spatial planning by using any analytical function (Loucks and da Costa, 1991). However, the decision makers need a responsible user friendly system to meet the faster, accessible and accurate spatial information of better sustainable planning. The development of Spatial data infrastructure (SDI) that nationally link the geospatial data among institutions may pave the ways to the development of thetool that can utilize all of those geospatial data. In this case, the development of the Geospatial Decision Support Systems (GDSS) as a tools for online assessment of sustainable marine spatial planning has to be developed in advance. GDSS contains model, data and interface appropriate for the issues being address, which promote and encourage interaction and feedback, dynamic and responsive to changes and lead to the better results (Loucks and da Costa, 1991).

This study aims to assess the development of GDSS for marine planning purposes in the frame of National Spatial Data Infrastructure. The method of GDSS development was based on System Development Life Cycle/ SDLC, Roebuck 2011), the analytical function of the model for GDSS was developed based on weighing factors, and the evaluation of the model was employed based on the expert system and convolution matrix. The result indicates that GDSS as part of the national SDI may increase the utilization of available dataset. However, its integration need more policy management issues rather than technical one. The model that was developed in the GDSS has to be open-ended design to facilitate the differences among regions and even though the validation of the system is almost 85 % true but the policy management issues for still become the main factor for successful implementation of the system.