Applying RNA interference to silence a specific gene has opened a new and promising avenue of gene therapy. But a key bottleneck is the poor stability and inability of naked siRNA to translocate through cell membranes. Among several delivery systems, cationic peptides capable of penetrating cell membranes have drawn attention due to their structural and functional versatility, potential biocompatibility and ability to target cells. In this review, different classes of peptides employed in siRNA delivery are reviewed. In particular, a new class of siRNA delivery peptides with high transfection efficiency and low cytotoxicity is introduced.