As an important part of academic papers which comply with the norms of social science research,citations themselves are of great research value . On the basis of the collection of citation data from top Chinese journals in economics,sociology,law and politics and on the basis of internal and international comparison research,we find that economics and sociology are more open to research abroad while law and politics are less open . And in these subjects,the level of citations to other social sciences is comparatively low . We also find that the percentage of self-citation in economics decreased significantly while that in sociology,law and politics increased moderately between 1998 and 2008 according to the results of the comparison of interdisciplinary citations . On the other hand,the percentage of interdisciplinary citation of sociology and law to economics are quite high,while the percentage of interdisciplinary citation of politics to economics is low . We think that the lack of interdisciplinary journals and the lack of researchers are two key reasons for the underdevelopment of interdisciplinary research in China .