Brown adipose tissue (BAT) is an ideal target organ for obesity treatment. Resinacein S is extracted from Ganoderma lucidum and can elevate Uncoupling protein 1 (UCP1) in cells, but its related effects at the animal level are not clear. The mice were fed with high-fat diet to construct obesity models and treated with Resinacein S. Fasting blood glucose and insulin concentrations were measured. The blood glucose changes were recorded by injection of glucose and insulin and the body temperature during cold stimulation were recorded. BAT was weighed and stained with HE. The blood lipid metabolism indexes were detected by kits and the UCP1 level was tested. Resinacein S could improve the obesity of mice, lower the body weight, fat weight, fat cell diameter and size, reduce fasting blood glucose, improve dyslipidemia, hyperinsulinemia and insulin resistance, enhance the tolerance to cold stimulation. After UCP1 knocking out, the body weight and blood glucose levels were raised, the blood lipid disorder was aggravated and the heat production and BAT activity of mice were decreased, while Resinacein S up-regulated UCP1 level and activate BAT activity. Resinacein S can improve obesity in mice by up-regulating UCP1 expression to activate BAT activity.