Stomata are the pores on leaf surfaces controlling gas exchanges, mainly CO_2 and water vapor, between the atmosphere and plants, and thus regulate carbon and water cycles in various ecosystems. This study investigated the effects of experimental warming on the stomatal frequency, stomatal aperture size and shape, and stomatal distribution pattern, and their relationships with the leaf gas exchange rates of maize (Zea may L.) leaves through a field manipulative warming experiment with infrared heaters in a typical agriculture ecosystem in the North China Plain. Our results showed that experimental warming had little effect on stomatal density, but increased stomatal index by 12% (P<0.05) due to the reduction in the number of epidermal cells under the warming treatment. Warming also decreased stomatal aperture length by 18% (P<0.01) and increased stomatal aperture width 26% (P<0.01). As a result, experimental warming increased the average stomatal aperture area by 31% (P<0.01) and stomatal aperture circumference by 13% (P<0.05), and resulted in a more regular stomatal distribution on both the adaxial and abaxial surfaces in leaves with an increased average nearest neighbor distance between stomata. In addition, experimental warming also affacted the gas exchange of maize leaves. Experimental warming significantly increased net photosynthetic rate (P_n), stomatal conductance (G_s), and transpiration rate (T_r) by 52% (P<0.05), 163% (P<0.001), and 81% (P<0.05), respectively. Meanwhile, experimental warming decreased the leaf dark respiration (R_d) by 24% (P>0.01), but had no significant effects on intercellular CO_2 concentration (C_i) and water use efficiency (WUE; P>0.05). In conclusion, the experimental warming may affect the gas exchange of maize leaves through the changes of the stomatal traits including stomatal frequency, stomatal aperture size and shape, and stomatal distribution on leaves.