In this paper we present a data migration method for developing GIS-based Fisheries Resources Information Systems after considering standardization of existing methods and analyzing characteristics of such systems. First, a strategy for data migration is defined. Second, a iterative process to build a spatial database is planned. Third, the process is executed to make database transformations and basic data are converted into real GIS data. Finally, developers and users cross-check data correctness. As a result of our research, we suggest a data migration method for GIS data and confirm its usefulness by applying it to real projects.