A slow-release membrane-encapsulated urea fertilizer with a superabsorbent and moisture preservation was prepared by cross-linked starch (the first layer), acrylic acid (AA) and acrylamide (the second layer; AM), ammonia, borax, urea, and so on. The variable affecting the water absorbency was investigated and optimized. The water absorbency of the product was 80 times its own weight if it was allowed to swell in tap water at room temperature for 80 min. Elemental analysis results showed that the product contained 26.74% nitrogen. The water retention property of the product and the slow-release behavior of nitrogen in the product were also investigated, and the results showed that the product not only had good slow-release property but also excellent water retention capacity. This will efficiently improve the utilization of fertilizer and water resources at the same time.