Abstract: The objective of this study was to define further characters of water consumption and physiological responses at different soil humidity in naked oat. Pot experiment I was conducted to investigate transpiration coefficient among naked oat, maize, sorghum, barley and spring wheat, and supplied water by a hydraulic pressure-controlled auto irrigator. In pot experiment II, three heights of pressure-adjusting pipe (i.e. 40, 60 and 80 cm) were used to make three levels of soil humidity (high humidity-moderate humidity-low humidity) to evaluate light responses and antioxidant enzyme activities of leaves at booting stage in naked oat. The results showed that the transpiration coefficient of naked oat was 455.37, significantly (P<0.05) higher than other’s crops. Lower soil humidity decreased SPAD, however, leaf photosynthetic ability was not significantly (P>0.05) restrained when appropriate to reduce soil humidity. Improving leaf water use efficiency was improved when appropriately increasing the degree of stomatal limitation. Leaf antioxidant enzyme activities showed different responses to three levels of soil humidity. SOD was significantly induced in moderate humidity, but POD and CAT were improved in high and low humidity, respectively. The results suggested that naked oat was a kind of crop required more water and low water use efficiency with higher stomatal conductance and lower net photosynthetic rate and leaf photosynthesis and antioxidant enzyme activities were not significantly decreased when reducing appropriately soil humidity.