Power grid analysis is a challenging problem for mod- ern integrated circuits. For 3-D systems fabricated using stacked tiers with TSVs, traditional power grid analysis methods for pla- nar (2-D) circuits do not demonstrate the same performance. An efficient IR drop analysis method for 3-D large-scale circuits, called 3-D voltage propagation method, is proposed in this paper. This method is compared with another widely used power grid analysis method, with preconditioned conjugated gradients. Sim- ulation results demonstrate that the proposed method is more efficient for the IR drop analysis of large size 3-D power grids. Speedups between 10× to 20× over the preconditioned conjugated gradients method are shown.