China and ASEAN are recognized as the most important markets in the world, hence they have emerged as global factories and parts production bases. And trade between China and ASEAN is rapidly expanding and ASEAN has taken position as one of Chinas three major trading partners. Over the last 20 years, there has been a rapid increase in intra-industry trade where differentiated products are traded within the same industries between China and ASEAN countries. Empirical analysis on determinants of the international specialization structure between China and ASEAN countries shows that the deepening structure of vertical international specialization between the two regions over the past 20 years has been directly influenced by variables representing national characteristics, such as distance (trading cost), common language, the size of the national economy and income gap as well as intra-regional foreign direct investment.