Leaf is the main organ for plant photosynthesis, respiration, and transpiration. Earlier studies mainly focused on water transportation pathway in leaves, but leaf vein architecture and its ecological significance have been rarely studied. Recently, studies of leaf vein architecture, functions of stomatal structure, and leaf hydraulic characteristics have become major focuses of plant ecological research. This paper reviews the index of leaf vein architectural traits (i.e., vein density, diameter, and distance between veins), the influence of leaf hydraulic characteristic on plant functions such as growth, water transportation, gas exchange, and the relationship between leaf hydraulic conductance and drought adaptability for plants. Leaf vein architecture is the foundation of leaf physiological functions, and future studies should explore various types of relationships between plant leaf vein architectural traits and functional characteristics such as hydraulic conductance, photosynthesis, and respiration. Future research might also aim at development of stem-branch-leaf continuum model to explore ecophysiological mechanisms of plant functional structures and efficiency of water transportation, and to assess the adaptation of plants to the future climate scenarios.