A double-ring resonator temperature sensing system based on a multiwavelength Brillouin fiber laser (MBFL) is proposed and demonstrated experimentally. In the two ring resonators, a 3.2-km long dispersion shifted fiber is used as the sensing fiber while a 3.2-km long dispersion compensating fiber is the reference. Second-order Stokes light generated by two gain fibers are used as the beat frequency to obtain the microwave signal. The frequency of the signal is 1.657 GHz, which avoids the low frequency noise region, and the signal has a high signal-to-noise ratio of 39 dB. A change in the center frequency of the beat frequency microwave signal accurately corresponds with the temperature changing. The sensitivity of temperature is 2.26  MHz  /    °  C in the condition of the sensing temperature being from 5°C to 85°C and the reference temperature being 25°C. Obviously, the MBFL can sense temperature not only below the reference but also above it; thus the scheme has a larger temperature sensing range.