Free-trade ports (FTPs) have become a means for China to promote economic upgrading, expand international trade, and attract foreign capital. Based on the variables of GDP, distance, language synergy, border conditions, and the exchange rates of trading countries, hypotheses are proposed regarding the influence of Chinese FTPs on the total import and export volume of foreign trade. The gravity model and convergence analysis are established based on the variables, and regression results are obtained using a varying coefficient model with panel data. The Levin-Lin-Chu test is used to test the hypotheses. Based on the results, it is concluded that the GDP, geographical distance, language synergy, and border conditions of Chinese FTPs and target countries significantly affect the import and export volume of foreign trade. Based on the findings, we make five suggestions for increasing the locational value of FTPs.