Abstract: Chemical fertilizers have been widely used for crop production in recent years. However, the current utilization rate of chemical fertilizers is generally low. Particularly, the excessive application has also led to the enrichment of the soil nutrients in the short term, far exceeding the nutrient requirements of plant growth. This nutrient imbalance can cause a serious waste of the fertilizer resources, and a series of chain environmental issues, such as soil compaction, microbial imbalance, ammonia volatilization, and nitrogen leaching. Multiple threats have been posed to the ecological environment. In this study, a composite coated urea was prepared to match the nutrient demand of the crops using slow release, in order to improve the soil water use efficiency with the help of the water retention function. The superabsorbent polymer (SAP) in the laboratory was used as the outer coating. The inner coating was taken as the polyurethane that was synthesized by polymethylene polyphenyl polyisocyanate (PAPI) and castor oil (CO). The composite coated urea (PCUB) was prepared with multiple functions, such as water retention and slow release. A systematic investigation was made to explore the effect of the amount of SAP on the slow release and loss control performance of the fertilizer. The number of days was 65 days for 80% slow release of polyurethane-coated urea without SAP (PCU). The PCUB with 5% SAP (PCUB5) effectively prolonged the slow-release period of fertilizer to 72 days. The hydrogel layer was formed into a three-dimensional network structure. The nitrogen release was then delayed after water absorption. The SAP significantly increased the water absorption of the fertilizer. Specifically, the water absorption of the PCUB5 reached 16.53 g/g. The experimental results showed that the ammonia volatilization of the PCUB5 treatment group was 17.65% lower than that of the PCU ones within 30 days, and 76.67% lower than that of the pure urea ones. At the same time, the soil with the PCUB shared a significant increase in the water holding and retention rate. Therefore, the SAP enhanced the soil water interception and then extended the effective water supply cycle of the soil. The soil column leaching experiment shows that the 30-day total nitrogen cumulative loss concentration of the PCUB5 treatment group was 79.03% lower than that of the pure urea treatment group. The field experiment showed that the PCUB5 treatment group, with a 20% reduction in dosage, significantly improved the growth performance of the summer maize, compared with the pure urea treatment. Among them, the plant height, stem diameter, chlorophyll content, dry matter content, and yield increased by 4.37%, 5.59%, 4.9%, 6.71%, and 24.7% (P<0.05), respectively. The nitrogen release cycle of the PCUB was more suitable for the nutritional needs of the summer maize. The synergistic effect of the hydrogel barrier and hydrogen bond can greatly contribute to the nitrogen release and crop fertilizer requirement cycle. The water-fertilizer regulation can provide a promising solution to sustainable agriculture in the arid areas. The nutrient release cycle of the PCUB can fully meet the nutritional needs in the growth cycle of the summer maize. The yield of summer maize can be significantly enhanced under the condition of reducing the 20% urea. A kind of fertilizer product can also be obtained with excellent prospects.