In distributed optical fiber sensing system of BOTDR, the frequency of the backward Brillouin scattering signal is modulated by temperature and strain, so the frequency of the signal can be attained with optical fiber to realize the temperature and strain measurement in remote. While, the scattering signal is very weak, the noise is large, and have a frequency width of several decades megahertz. In tradition, the complete high-frequency Brillouin scattering signal is obtained by adopting the method of frequency scanning which capture the frequency in section through changing the rate of sweep frequency module. And then, using multiple averaging measurement to reduce noise. But it is difficult to acquire the signal rapidly and eliminate the interference of noise. Therefore, an edge filter approach is proposed in this paper to get the whole scattering signal, which convert the frequency information into energy message. In order to better represent the effectiveness of this method, an experiment were taken. And the result shows that: SNR had been greatly enhanced, sampling time was reduced to the cost of getting one frequency point when using frequency scanning. It demonstrate that the proposed method can collect the signal quickly and be beneficial to demodulate temperature and pressure in time.