Abstract:  Transesterification of Swida wilsoniana oil with methanol to biodiesel was conducted by using the immobilized lipase Lipozyme TL IM as the catalyst in MgCl₂-saturated solution. The effects of alcohol/oil molar ratio, immobilized lipase loading, agitation speed, and reaction time on the transesterification were investigated. The yield of biodiesel reaches a maximum value of 86.5% after reaction for 8h under the optimal conditions: methanol/oil molar ratio of 3, 20% of Lipozyme TL IM based on Swida wilsoniana oil, and agitation speed of 150r/min. Compared with the traditional transesterification methods like using 3-step methanolysis or with tertiary butanol as solvent, the problem of immobilized lipase inactivation is solved effectively by using the MgCl₂-saturated solution. Moreover, the current process has potential for biodiesel production owing to its improvement in lipase stability, reaction efficiency, and production costs.