To improve the Brillouin optical time domain analysis (BOTDA) system performance limited by signal noise, we proposed a noise reduction method based on complete ensemble empirical mode decomposition with adaptive noise combined wavelet threshold (CEEMDAN-WT). First, the noise reduction principle of CEEMDAN-WT algorithm is analyzed. Besides, the BOTDA signal demodulation model is set up based on the principle of microwave sweep frequency measurement. The simulation results show that CEEMDAN-WT method can remove the random noise in the signal effectively. Then, the BOTDA system is set up for temperature measurement. The CEEMDAN-WT method is adopted to suppress the noise of each measured power curve at different sensing distances and different spatial resolutions. Finally, the experimental results show that the signal-to-noise ratio ( SNR) at the end of the optical fiber is improved by 8. 89 dB utilizing the CEEMDAN-WT noise reduction method, under the sensing distance of 30 km and the spatial resolution of 2 m. Research show that the CEEMDAN-WT method provides an effective scheme for improving the SNR of BOTDA.