The nitrogen release characteristics of silicon-based membrane slow-release fertilizer under different soil temperature，water content and vapor pressure conditions were studied by soil cultivation and saturation salt solution vapor pressure method. The effects of soil temperature， water content and water vapor pressure on nitrogen release were discussed， and the controlled-release mechanism in red soil was expounded. The results showed that the nitrogen release rate of silicon-based membrane slowrelease fertilizer in red soil increased significantly with soil temperature， water content and water vapor pressure increasing. The most important factor was soil temperature. The nitrogen release rate of coated fertilizer with cultivation time followed the first-order kinetic equation under different conditions. Coated urea time required was 140， 110， 25 and 10 d in red soil at 15， 25， 40 and 60℃， respectively， when the cumulative nitrogen release rate was 80% of the total. Nutrient release was inhibited when soil water content was 10%. The nutrient release rate accelerated and the release period was shortened by 20 d when soil water content raised from 20% to 40%. The nutrient release rate constant k increased with the water vapor pressure deficit increasing. For the same cultivation time， the nitrogen accumulation release rate showed as the saturated solution of H2O>KH2PO4 saturated solution>KCl saturated solution. Soil temperature and water content can change the water vapor pressure inside and outside the membrane， and then affect the nutrient release rate. In the practical application， the factors that cause the change of water vapor pressure inside and outside the membrane of silicon-based membrane slow-release fertilizer will all affect the nutrient release rate.