Based on the micron level size of microencapsules prepared by In-situ polymerization method with urea formaldehyde resin as wall material,nano-capsules were prepared with urea-formaldehyde resin as shell,sandalwood fragrance as core and Tween80 as emulsifier.Shell/core ratio, size of emulsified essence,solid content were studied as single effect factor .Three factors’ level was ranged by evaluation of particle size and distribution.It showed that when the system solid content was less than 1%, shell/core ratio of 2:1-5:1, emulsified fragrance particle size for 50-200 nm,well-distributed nano-capsules can be obtained. A quadratic polynomial model between the size of UF partials and the three factors was established by using response surface methodology.In addition, R2 value of the model is 0.9927,while the relative deviation of the verification experiment were within 6%,which showed the model to have good effectiveness in predicting protease production.