This paper reported phase jumps in the process of Stimulated Brillouin Scattering. The jumped probability with the incident energy was measured. The result showed that the jumped probability in the medium CCl 4 is about 20%. Even if the incident energy is saturated, phase jumps still exist. Phase jumps disrupt the phase of the Stokes beam generated by SBS, therefore tend to decrease the coherence length, increase the spectral width of the Stokes signal, suspend the phase conjugation process and decrease the fidelity of phase conjugation.