To simplify the system structure and reduce the effect of coherent Rayleigh noise on system performance, a temperature sensing system based on Brillouin optical time domain reflectometry by employing broad-band laser and self-heterodyne detection of Rayleigh and Brillouin scattering was proposed. The principle of self-heterodyne detection of Rayleigh and Brillouin scattering was analyzed, and the relationships of Brillouin frequency shift and self-heterodyne detection signal power with temperature and strain were studied. A temperature sensing system based on Brillouin optical time domain reflectometry by employing broad-band laser and self-heterodyne detection was designed and constructed, the power spectrum of self-heterodyne detection signal along the sensing fiber at room temperature and the power spectra of the heated fiber at different temperature were obtained. The linear increase relationships of Brillouin frequency shift and change in relative self-heterodyne detection signal power with temperature were demonstrated. The temperature coefficients of Brillouin frequency shift and change in relative power were experimentally obtained to be 1.07±0.01 MHz/℃ and (0.37±0.09)% /℃. The results of this study can provide a theoretical and experimental basis for the simultaneous measurement of temperature and strain of Brillouin optical time domain reflectometer sensing system based on self-heterodyne detection of Rayleigh and Brillouin scattering.