基于FLAC3D内置的FISH语言，对其渗流模型进行了扩展。将实验室测得的原状黄土土水特征曲线，利用MATLAB实现了参数拟合。将拟合参数编写为子程序，在每步渗流分析中加以调用，从而实现非饱和土的渗流模拟。利用该方法与有限元法分别模拟3种边界条件下的一维入渗问题，并比较模拟结果。经验证，结果吻合。其结果对研究非饱和土理论及扩展FLAC3D在非饱和土数值计算方面的应用均具有一定的意义。

The seepage model in FLAC3D was extended using its in-built programming language FISH. The SWCC (Soil Water Characteristic Curve) for seepage in unsaturated loess was best-fitted using MATLAB. The obtained parameters were written as a subroutine and invoked in each step in the seepage model of FLAC3D to simulate the unsaturated loess. One-dimensional infiltration problem in three boundary conditions was modeled using both the finite difference method and the finite element method to verify the extension in FLAC3D. The comparison results show that the above method is appropriate. The findings of this paper are meaningful in the investigation of the unsaturated soil theory and in the application of FLAC3D to simulate unsaturated soil problems. 