Abstract: A new type of negative hydraulic pressure controlled auto irrigator was used to designed different levels of water supply tension to control different soil moisture regime. The objective was to study physiological growth of corn(Zea mays L.) and soil water conservation using water-retaining agent under three irrigation levels(3, 6 and 9 kPa). Under 3 kpa, plant height decreased by 7.4%, leaf area decreased by 14.9%, shoot dry weight decreased by 12.4%, root dry weight decreased by 7.3%, the water use efficiency decreased by 12.6% due to application of SAP. Under 6 and 9 kpa, plant height increased by 10.0% and 37.9%, leaf area increased by 14.2% and 90.8%, shoot dry weight increased by 40.4% and 104.6%, root dry weight increased by 35.3% and 83.8% respectively, the water use efficiency increased by 26.9% and 65.7% substantially respectively for SAP application. At the same time, leaf water potential exceeded that without SAP by 7.1% and 19.2% respectively. Higher relative water contents in leaves as well as intercellular carbon dioxide concentration, net photosynthesis and transpiration rate was maintained. Our results indicated that SAP can improve physiological growth of corn and increased its water use efficiency under water limited condition.