Regionalization is a common method for prediction in ungauged basins (PUB), and it is one of the research hotspots in recent 20 years. This paper introduced the current international research on regionalization in solving PUB problem, to provide reference for domesti c research. This paper divided re gionalization into 3 categories, namely, regionalization based on spatial distance, regionalization based on hydrological similarity and regionalization based on regression. By literature review and case analysis, the problem and the scope of application has been analyzed. At last, this paper pointed out 5 problems in the PUB in China.