In recent years, with the rapid development of economic globalization, China started to implement tree trade area (FTA) strategy, and the speed and scale attracted lots of the attention. Based on traditional gravity model, this paper adds variables such as tree trade agreements to establish an extended gravity model to analyze various factors' impact on China's trade flows. The empirical results show that the economic scale of the trading nations or regions, population, culture and trade arrangements are the main factors to affect China's trade flow. The establishment of free trade area exposes a positive effect to a certain extent, while distance still plays a significantly negative role. In addition, on the matter of tree trade agreements, trading partners' economic scale also has a negative correlation with trade flows. These conclusions may be expected to provide some policy suggestion for the further development of Vietnam FTA.