清代数学家项名达在中国数学史上首次给出了计算椭圆周长的正确公式,这一公式与椭圆积分法所得结果完全一致。本文较全面地分析和讨论了项氏推导这一公式的过程及思想方法,认为项氏的工作是清代数学史上一项重要成就。过去对项氏椭圆求周公式推算过程的解释有某些不妥之处,本文对此给予了辨证。 For the first time in the history of Chinese mathematics, the name of the mathematician in Qing Dynasty gave the correct formula for calculating the circumference of an ellipse. This formula is exactly the same as that obtained by the ellipse integration method. This article analyzes and discusses the process and method of deriving this formula in a comprehensive way, and holds that the work of Xiang is an important achievement in the history of mathematics in the Qing Dynasty. In the past, there were some shortcomings in the explanation of the process of calculating the formula of the ellipse of the Xiang’s ellipse. This article gives dialectical evidence.