Abstract: The mechanisms of interspecific competition and complementarity and the characteristics of water utilization in intercropping system are reviewed in this paper. Meanwhile, key research fields related to intercropping in the future are prospected. Intercropping system can increase water use efficiency (WUE) of crops, and is in favor of providing an optimum soil moisture environment for crop development. Competition and complementarity are two aspects of the same interspecific relationship; quantifying competition and complementary effect of intercrops on soil resources is an important topic in intercropping system. The main influence factors for interspecific competition and complementarity in intercropping system include crop species, planting density, spatial arrangement, and environmental factors. Interspecific competition and complementarity are leading factors influencing water utilization of intercrops and studies on synergistic effects of competition and complementarity in intercropping systems are limited. Prospective future research fields are identified as follows: (1) To determine the dynamics of dry matter accumulation, allocation and irrigation water productivity, to study compensation effects on water use in latematuring crops after the earlymaturing crops were harvested in intercropping systems, and to clarify the correlation between WUE of crops and interspecific interaction. (2) To investigate spatiotemporal dynamics of soil water potential and available soil water, and to analyze the relationships among soil water movements within interspecific competition and complementarity, in order to provide theoretical basis for optimizing interspecific competition and complementarity under irrigation regulations. (3) To evaluate the effects of intercropping on crop moisture physiological and ecological characters so as to reveal the complementary mechanism of interspecific interaction with respect to hydrophysioecological viability. (4) To explore the correlations between rootshoot equilibrium and spatiotemporal distribution of root, as well as water use characteristics and interspecific competition and complementarity, to elucidate how the rootshoot equilibrium works on improving WUE via the synergistic effects of inter specific competition and complementarity. By integrating the main results at different scales, theoretical basis for enhancing WUE of intercropping through regulating interspecific interactions could be established, which provides support for development and extension of intercropping systems in waterdeficient areas.