What effect does a weakening US dollar (USD) against RMB have on Sino-South Korea bilateral product trade during 2002-2013? This paper uses statistical comparison and GMM estimation to show that firstly, along with a weakening US dollar, we find no obvious evidence of China’s export deflection to South Korea (SK), whereas SK obviously increases the share of product export to China. Along with a weakening US dollar, there are higher product trade complementarities and lower product trade competitiveness between China and South Korea. Secondly, following a weakening US dollar, real depreciation of RMB/Won exchange rate of goods is bad for China’s product export to SK, and does not bring about the increase of China’s real import from SK. In the meantime, real depreciation of RMB/USD exchange rate is harmful to China’ s export to the US, In addition, it does not bring about the export of China’s deflection to SK, but reduces China’s import from SK. The rise of RMB/Won real exchange rate volatility can bring about significant and adverse impacts on Sino-SK bilateral import and export, whereas economic growth in the two countries can enhance significantly Sino-SK bilateral trade. Therefore, some policy suggestions are that it is very important to establish and deepen Sino-SK Free Trade Area to expand trade markets. The two central banks increase the currency swap scale, and create new financial instruments to reduce exchange rate risks, which promotes Sino-SK bilateral trade to the utmost.