An analysis of the regional specialization trend in China since the beginning of its economic reform in 1979, and the determinants of this trend. The indices of regional specialization are calculated for years 1985 to 2006. Important policy changes during this period, mainly agricultural policy changes, are discussed. After applying the fixed effect regression on a modified Heckscher-Ohlin model, it is found that: (a) among scale, natural resource and human investment variables, only human investment are significant; (b) WTO membership has had a positive total effect on regional specialization of China's agricultural production; (c) Regions that produce a larger portion of exportable products have become more specialized since entering WTO; (d) Center region of China is the one with the least specialization.