数值分析中，交替方向隐式法（Alternating direction implicit method）是有限差分法的一种，用于求解抛物线型偏微分方程或椭圆型偏微分方程。特别适用于求解二维及更高维度的热传导方程与扩散方程。

求解热传导方程在传统上使用Crank-Nicolson方法，该方法较为耗时。ADI的优点在于，每一迭代步中，所求解的方程具有更为简单的结构，因此更易于求解。

In numerical analysis, the Alternating Direction Implicit (ADI) method is a finite difference method for solving parabolic, hyperbolic and elliptic partial differential equations. It is most notably used to solve the problem of heat conduction or solving the diffusion equation in two or more dimensions. It is an example of an operator splitting method.