This research examines the trade mode between mainland China and Hong Kong, and empirically studies the bilateral trade panel data of China’s 29 provinces and Hong Kong in 1997-2011. Moreover, both Guangdong and Hong Kong’s trade effect since CEPA’s signature is analyzed. The results show that the trade scale is proportional to GDP, but is in inverse proportion to the per capita income gap between Hong Kong and mainland China. Also, the CEPA promotes two-way trade significantly while the economic crisis decreases bilateral trade flows to some extent. Besides, both Guangdong and Hong Kong have gained trade creation effect since CEPA was signed.