The technique of multi-wavelength laser source is introduced into Rayleigh Brillouin optical time domain analysis system, in which multi-wavelength Rayleigh back-scattering generated by the 1st-order side-band of suppressed carrier microwave-modulated multi-wavelength pulse base is used as probe light to interact with the multi-wavelength sensing pulse through stimulated Brillouin scattering (SBS). The interaction can effectively improve the fiber SBS threshold, SBS interaction efficiency, and measurement precision of signal-to-noise ratio and Brillouin frequency shift. The generation principle of the multi-wavelength laser source by phase modulator and the exciting source of multi-wavelength Stokes light and anti-Stokes light used as probe light in the system by electro-optic intensity modulator is analyzed. The multi-wavelength Rayleigh Brillouin optical time domain analysis system is characterized by modeling analysis, in which the relationship between the signal-to-noise ratio and the wavelength number is achieved. Then a fiber SBS threshold measurement system and a Rayleigh Brillouin optical time domain analysis system using single-wavelength and three-wavelength laser sources are designed and the fiber SBS threshold and the system performance are tested. Experimental results show that when the fiber length is 2.4 km, the sensing pulse is with a width of 100 ns and a power of 100 mW, and the pulse base is with a power about 1.3 mW for each wavelength component in the single-wavelength and the three-wavelength systems, the fiber SBS threshold and signal-to-noise ratio in three-wavelength sensing system are approximately to be as high as 3 times and 2.83 times than that in single-wavelength sensing system, respectively. And within 2 km fiber length, the Brillouin frequency shift fluctuation decreases from 33.4 MHz in single-wavelength sensing system to 15.6 MHz in three-wavelength sensing system.