Base on three-year eddy covariance system measurements, environmental controls on rainfed maize cropland have been analyzed. The results show that energy factors (radiation and temperature) and water conditions (rain, soil moisture, and vapor pressure deficit) are crucial to water and heat exchanges in different ways. The effects of energy factors on water and heat exchanges are gradually weakening with increasing time scales. While, change in the impacts of water conditions on water and heat exchanges in inverse way. In different hydrological years, there are significant distinctions in environmental controls on water and heat exchanges. In humid year, available energy is primary controls on water and heat exchanges without water stress; and in arid year, available energy and soil moisture all strongly affect on water and heat exchanges.