Abstract: The range of Yangtze River Delta economic integration has extended from the original 16 cities to the whole areas of Jiangsu province, Zhejiang province and Shanghai city since 2008, which provides useful cases for the exploration of the boundary effect of domestic regional economic integration and the policy effectiveness. By making use of the data of prefecture-level cities in Yangtze River Delta during 2001-2012 and with the help of Barro’ convergence regression equation, this paper tries to test the boundary effect of the regional economic integration, the scope expansion effect of the integration, the policy effectiveness of the scope expansion and the regional economic growth convergence respectively. The results show that there is significant boundary effect between the core of the Delta and its periphery. After the expansion, from the viewpoint of economic scale changes, there is significant negative boundary effect; from the viewpoint of labor productivity changes, there remains significant positive boundary effect, so the boundary effect does not disappear. The regional economic integration in Yangtze River Delta is earlier than the time of policy promulgation of the scope expansion, so that, the policy has the characteristics of adaptive policy adjustment. Thus it can be seen that the industrial agglomeration and diffusion in the process of the unbalanced development of regional economy is one of the causes of the regional boundary effect, the regional coordinated development policy cannot completely eliminate the boundary effect.

Key words: scope expansion of Yangtze River Delta; boundary effect; policy effectiveness