The availabilities of nitrogen (N) and water are two important environmental factors affecting crop growth and productivity in the dryland farming, how they affected leaf water transport capabilities, a bottleneck of whole-plant water transport, was seldom studied. So, the effects of different N and water supplies on leaf hydraulic conductance (K-leaf) in maize (Zea mays L.) were studied by a pot experiment, K-leaf, leaf gas exchange, vein traits and other physio-anatomical traits were measured. We found K-leaf was strongly coupled to leaf gas exchange (net photosynthetic rate, P-n, and stomatal conductance, g(s)) and whole-plant performance under varying N and water supplies. Long-term N supply had a greater impact than irrigation on K-leaf, P-n and g(s) due to the type and duration of stress, and the N and water treatments did not interact with these physiological parameters. K-leaf was related positively with the xylem conduit diameter of large longitudinal veins, the proportion of minor-vein length and interveinal distance of large and intermediate longitudinal veins, and negatively with the density of the major veins, and the interveinal distance of the transverse veins. The higher K-leaf under ambient N and water supply was also associated with larger leaf area, leaf mass per area and N content per leaf area and with an improved status of leaf water, which partly enhanced the vein traits responsible for the higher K-leaf. These results are helpful to understand leaf hydraulic strategy in adapting to long-term resource deficiency.