In order to reduce the fitting error caused by the broadening of the spectrum, this paper proposes to use the double-sideband continuous light as the detection signal and use its interference spectrum for sensing. Compared with the traditional Brillouin gain spectrum, the obtained spectrum has a narrower linewidth near the resonance spectrum, the error of the double-peak fitting in the pre-pump temperature sensor is reduced, and the frequency resolution of the system is improved, so as to achieve high spatial resolution and high frequency resolution of a pre-pump Brillouin optical time domain analysis （BOTDA） system based on double-sideband interference. Experimental results show that 50 cm spatial resolution and 0.37 MHz frequency resolution can be achieved on 100 m polarization maintaining fiber by using this method. Compared with the traditional single side band pre-pump system, the frequency resolution of the system is increased by 2 times under the same spatial resolution.