Objective To investigate the effect of Qi-boosting & Yin-nourishing formula and purslane herb on expression of nitric oxide synthase (NOS) positive neuron in hippocampal CA1 area of diabetic rats. Methods The diabetic rat models were induced by intraperitoneal injection of streptozotocin. After prevented and treated with Qi-boosting & Yin-nourishing formula and purslane herb one month, the diabetic rats were killed, the expression of NOS was detected by NADPH-diaphorase histochemistry. Results The expression of NOS positive neuron in hippocampal CA1 area of diabetic rats which were prevented and treated with Qi-boosting & Yin-nourishing formula and purslane herb was increased (P