Abstract: Objective: The aim of this study was to observe the role of L-NMMA in the areterioles vasomotion induced bynoradrenaline（NA）,in order to make further understand of mechanism of vasomotion induced by NA. Methods: Albino rabbitsweighting 2.0～2.5 kg were anesthetizedwith urethane（0.75 g/kg）and alpha-chloralose（30 mg/kg）intravenously. The rabbits were ventilated with room air via tracheotomy tube. The arterial pressure was monitoredwith a pressure transducer attached to a polyethylene canula in the right common carotid arteryby four channel polygraph,the intestinal loop was mounted on the stage of an invertedmicroscope and bathed in balanced Kreb-Ringer solution maintained at 37.5℃.The inside diameter of arterioles were measured manully on a TV monitor using a TV camera mounted on the microscope. Observe the changes of BP and microcirculation after injection of NA intravenously. L-NMMA（10mg） were administered via a cannula in the left carotid artery after topical application of NA（0.8g） conducted in the measured field. Results: Spontaneous vasomotion which has freqency and amplitudecan be induced in the measured field after NA topically used. L-NMMA can inhibit vasomotion in vasoconstrictionstage. Conclusion: NO may participate in the mechanism of vasomotion induced by NA.