Abstract: Based on the starch water retaining agent(SWRA),the water retention capacity and capacity were measured.The result showed that the performance of SWRA was affected by water medium,pH value,fertilizer fluid and soil environment.The SWRA is unsuitable for high salt content of soil.The water absorption rate decreased with the concentration of NaCl increased.The water absorption rate is highest at pH 6.5.The urea has the best water absorption in nitrogen fertilizer fluid.The loam has better repetitive water absorption capacity.When the water content of loam is 75%,the water retention is the best.