Employed the all-fiber Mach-Zehnder interferometer, a distributed optical fiber temperature sensing experiment system based on spontaneous Brillouin (BOTDR) was presented, and a temperature measurement signal with spatial resolution of 20 m was obtained. The system noise was analyzed and found that the measuring system is greatly influenced by the photoelectric detector noise. For improving the SNR (signal noise ratio), the method of wavelet analysis was brought to remove the noise of the system, and the suitable wavelet functions are selected. The result of wavelet denoising the noisy signal shows that, the sym wavelet can distill the temperature information even if it’s submerged in the noise. The method can improve the system’s ability of resistant to noise which introduced by photo detector effectively,and the measurement period is reduced comparing with the average method, which improved the real-time performance of the system.