The article explores how China's regional economy has opened up to both inter-regional and international trade, focusing on the manufacturing industry. The researchers studied the factors influencing the concentration of manufacturing industries in different regions at three levels: overall, inter-provincial, and over time. They found that regions with double opening policies show a clear concentration of manufacturing industries. Before joining the WTO, international trade had a bigger impact on manufacturing concentration, but after joining, inter-regional trade became more influential. This shift aligns with China's evolving approach to opening up its regional economy.