基于旋转流体地球内部的等密度面与等重力势面重合原理，建立决定地球内部等重力势面参数的微分方程．使用目前国际上公认的地球模型，通过对该微分方程的数值求解获得旋转地球形状参数的理论值，并与实际值进行比较．对比发现，本文导出的微分方程比现有相关微分方程的求解结果更接近实际值，更适合作为研究地球形状的基本方程．由于微分方程的建立过程非常复杂，尝试以适应教学的方式进行叙述，并省略那些繁琐的数学公式，重点介绍物理思想和解决方案，以及数学推导中的关键步骤、结点以及重要公式、结果，努力实现文章的教学研究性与科学研究性二者的统一．

Based on the principle of coincidence between the surfaces of equal density and the surfaces of equal geopotential inside the rotating fluid Earth, a differential equations is established to determine the parameters of the surfaces of equal geopotential inside the Earth. Using internationally recognized Earth models, obtain theoretical values of the shape parameters of the rotating Earth through numerical solutions and compare them with actual values. Comparison shows that the solutions of the differential equations derived in this article are closer to the actual values than the solutions of existing related differential equations, and the differential equations in this article are more suitable as the basic equations for studying the shape of the Earth. Due to the complexity of the process of establishing differential equations, attempts are made to adapt the teaching approach and omit those cumbersome mathematical formulas. Emphasis is placed on introducing the physical concepts and solutions involved, as well as the key steps, key nodes, key formulas, and important results in mathematical derivation.