Essential oil was extracted from Lysimachia foenum-graecum Hance using steam distillation method. The extraction conditions of essential oil were optimized by orthogonal experimental design, and its preservation on longan was studied. The results showed that the optimum extraction technology were: the concentration of sodium chloride 4%, the distilling time was 6 h, and the solid-liquid ratio of 110 (g/mL). Under the condition, the extraction rate of essential oil reached 0.167 2%. The preservation results indicated: the antibacterial effects of 4 treatments, the content of Vitamin C and soluble solid decreased gradually, and weight loss and corruption rate of longan increased with the extension of the time. Its ability of antibacterial effects and preservation were followed: 0.5% essential oil ＞ the mixture of potassium sorbate and essential oil ＞0.05% potassium sorbate ＞75% ethanol. It has better preservation effect on longan of essential oil than potassium sorbate.