Abstract: The culture medium of Candida tropicalis sp. JM-1 isolated from wastewater was used as a demulsifier treating emulsion wastewater from a cold rolling plant. The emulsion wastewater was biodemulsified by 97.1% in 8 h at room temperature. The capability of the biodemulsifier was stronger than the chemical demulsifier SYM + PAC, and the biodemulsification process was less affected by the pH and temperature of wastewater. The biodemulsification capability mainly resulted from the biosurfactant produced by JM-1. The advantages of the biodemulsification are high demulsification rate, little sludge source, and without secondary pollution.