The Toona sinensis extract of the present invention is prepared using supercritical fluid technique, wherein the method includes steps of: (a) drying the leaves of T. sinensis; (b) pulverizing the leaves as particles; and (c) extracting the particles with supercritical carbon dioxide to obtain the T. sinensis extract. This supercritical T. sinensis extract not only can decrease blood sugar level, but also promotes lipid degradation, inhibits the formation of huge lipid droplet and improves the metabolic symptoms. Accordingly, the T. sinensis extract further is able to be prepared as food supplement and pharmaceuticals.