本文从退化壳理论[6]出发构造了任意曲面壳体的四边形有限元线法[1][2]单元。该单元满足 连续，为协调单元。对于所构造的单元，本文从最小势能原理出发推导出用该单元作壳体静力计算的控制微分方程和边界条件，得到一致的线法方程体系。全文共分两篇，此为上篇，主要介绍基本理论，数值算例将在下篇中给出。 Based on the degenerated shell theory [6], a quadrilateral finite element method [1] [2] with arbitrary curved shells is constructed. The unit to meet the continuous, for the coordination unit. For the unit constructed, this paper derives the governing differential equation and the boundary condition of the shell using the unit as the basis for the minimum potential energy principle, and obtains a consistent system of equations. The full text is divided into two parts, this is the first part, mainly introduces the basic theory, numerical examples will be given in the next part.