To investigate the two important characteristic parameters of threshold value and gain coefficient of Stimulated Brillouin Scattering (SBS) in water, the effects of temperature and salinity on SBS gain are analyzed theoretically, and meanwhile coupling wave equation combined with average attenuation coefficient are employed for analyzing the dependence of SBS threshold value on the temperature and attenuation coefficient of water. The results show that, SBS is positively correlated with temperature and salinity of water; the threshold value decreases with the increase of temperature and increases with the increase of attenuation coefficient. The results provide theoretical basis for understanding the SBS process in water.