采用有限元法建立了一种适用于求解平面二维恒定流场的数学模型．并提出了一种处理固壁不可入边界条件的方法。方程离散具有通用和严格的特点，对合成后形成的非线性方程组采用牛顿迭代法求解，一般仅需４～７次选代便能获得稳态解。模型除经过各种典型情况的考题试算外，还用长江中游界牌河段的实测资料进行了验算，结果与实测值符合良好。 The finite element method is used to establish a mathematical model suitable for solving two-dimensional constant flow field in the plane. And a method of dealing with solid wall inaccessible boundary conditions is proposed. Discrete equations are general and rigorous. The nonlinear equations formed after synthesis are solved by Newton’s iterative method. Generally, steady-state solutions can be obtained with only 4 to 7 generations of substitutions. In addition to the model after a variety of typical test questions, but also with the middle reaches of the Yangtze River boundary plate measured data were checked, the results in line with the measured values ​​in good.