中文摘要：

引力方程是一个被广泛采用的实证工具，其理论基础和估计方法一直是国际贸易领域的重要问题。理论方面，近来研究表明不同的贸易理论能推导出结构相似但比较静态含义不同的引力方程。实证方面，零贸易和内生问题的发现，使得传统估计方法不再适用。包括PPML和Heckman选择模型在内的许多新方法被提出并采用。

英文摘要：

Gravity equation is frequently used as an empirical tool. Its theoretical foundation and estimation methods have always been an important topic in the field of international trade. On the theoretical part, the recent studies find that similar gravity equations with dissimilar comparative static implications can be derived from different trade models. On the empirical part, traditional estimation methods perform poorly as a result of the occurrence of the problem of zero trade and endogeneity. Some new methods including PPML and Heckman selection model have been proposed and used. This paper aims to summarize and review the recent developments in this field.