Abstract: According to the observation of the data of trade between the Pearl River Delta and Hong Kong and Macao after the establishment of the PRC, we can see that the trade scale and structural changes have promoted the process of the integration of Guangdong-Hong Kong-Macao Bay Area. So, has trade played a role in the integration of Guangdong-Hong Kong-Macao Greater Bay Area? If so, how can trade play a role in promoting the process of integration as an integrated link in the development of the Greater Bay Area between Guangdong and Hong Kong and Macao? On the basis of summarizing the existing trade theory and empirical researches, the article develops a long-term dynamic theory of the trade's role in the integration and explains the process of the integration of Guangdong-Hong Kong-Macao Greater Bay Area. In this article, the process is divided into three phases of natural stage in chronological order since the establishment of the PRC to demonstrate the point above-mentioned. The first stage is the time after the founding of the PRC and before the reform and opening up. In this period, trade of goods dominated by primary commodities was the source of regional cooperation in Guangdong, Hong Kong and Macao. Since the reform and opening up, the Guangdong- Hong Kong- Macao regional cooperation has made great progress. The rise of cross-border production and trade with industrial transfer as the mainstay has greatly broken the bias of development between Hong Kong, Macao and the Pearl River Delta. The frequent exchanges between Guangdong, Hong Kong and Macao have led to the rapid economic growth of the three regions and the emergence of trade in the east and west of the Pearl River Delta. The phenomenon of industrial clusters has promoted the deepening of infrastructure in the three regions. In the third stage, starting from China's accession to the WTO in 2001, China's economy has been further more open to the world. Hong Kong and Macao, which have extensive experience in international standards, have become the vanguard of the country's active integration with globalization. In 2003, the Mainland and Hong Kong and Macao signed CEPA on the basis of improving the liquidity of commodity trade. Besides, a series of supplementary agreements have also promoted the flow of production trade and service trade from Hong Kong and Macao to the Pearl River Delta cities. With the close trade and service trade, the degree of innovation and knowledge spillover has also been enhanced. The conclusion of this paper is that trade has played a catalytic role in the process of the integration of Guangdong-Hong Kong-Macao Greater Bay Area. By changing the target of trade from goods to production and finally to service, the main body of trade, from physical goods to intangible goods, is the major process of promoting the integration of the Greater Bay Area of Guangdong, Hong Kong and Macao, from the primary to the more advanced one. In addition, the process of trade integration has a great spillover effect and it has perfected the regional basic road network. What’s more, the construction of industrial clusters has promoted the emergence of industrial clusters, boosted regional innovation and pushed the integrated area to a new platform for cooperation. The article summarizes the literature on trade and regional integration and would have some theoretical significance. Based on the summary of existing trade theories and empirical studies, the paper develops the conjecture on the dynamic role of trade in regional integration over a long period of time. And through the empirical demonstration of integration of Guangdong, Hong Kong, Macao Bay area, it has laid the foundation for the dynamic role of integration theory in the future study.

Key words: the Guangdong-Hong Kong-Macao Greater Bay Area, regional integration, trade, agglomeration, innovation