To realize the synchronous measurement of temperature and salinity of seawater, we study a data inversion method by combining frequency shift and line width of stimulated Brillouin scattering (SBS) theoretically and experimentally. Theoretically, the variations of frequency shift and line width of SBS with the changes in temperature and salinity are fitted by empirical formulas. Experimentally, the frequency shift and line width of SBS in seawater with different temperatures and salinity are measured, and then the temperature and salinity of seawater are analyzed by the theoretical inversion model. The results indicate that the simultaneous inversion of seawater temperature and salinity can be realized by the combination of frequency shift and line width of SBS. The minimum and maximum temperature inversion errors are 0.04 ℃ and 0.41 ℃, respectively, and the minimum and maximum salinity inversion errors are 0.09‰ and 0.65‰, respectively.