Abstract: To explore the mechanism of nitric oxide synthase(NOS) induced by marching tin dry hot desert,nitric oxide synthase(NOS)likein plasmas was detected.It was found that at 3.5km/h,the curve of NOS with marching time look like‘bell'.NOS in plasmas increased rapdly in the first hour,then decreased fast in second hour,after 2 hour,dropped slowly to the level of the control.At 5.0km/h,the courve of NOS with marching time is nearly a horizontal line.The NOS in plasmas decreased slowly within the first hour,then dropped fast to the bottom after 1 hour,and increased slowly to the level of the control.The results demonstrated that the consumption of NOS involved in the regulation of physiological stress increased with the speed, especially in the first 2 hour.After marching for 3 hour,the activation and consumption of NOS reformed a new balance.So,marching at 5km/h.is more appropriate in dry heat desert.