Abstract: Three substrates, sand, cinder and sawdust with different rates of water retaining agent(WRA) application, and flowering chinese cabbage as tested crop were used to study the effect of WRA on the water retention properties and bulk density of the substrates as well as the emergence and growth of the crop seedling. The results showed that the water holding capacity of the three substrates and the wet bulk density of sawdust were significantly increased along with the increase of WAR application rate, but the wet bulk density of sand and cinder were trended to decrease. WRA also could enhance the rate of emergence. As the increase of WAR application rate, the wilting time of the seedling was markedly prolonged and the plant height and biomass of the seedling were obviously increased. The water use efficiency of the crop increased only with the increase of WRA application rate under a certain level. However, when the rate overran the level the water use efficiency would decline.