Brown adipose tissue (BAT) is a special adipose tissue which burns fat and dissipates energy in heat. As a result, it is considered to be the next potential therapeutic target for treating obesity and other metabolic diseases. The ability of heat dissipation of BAT is thought to be highly related to the BAT activity. In this study, we intended to use MR thermometry to map the temperature change distribution in BAT after activated by Norepinephrine. The preliminary results show the PRFS based thermometry can observe the temperature change in BAT after activation, implying that MR thermometry might be a useful tool to characterize the BAT activity.