A method of using Brillouin scattering technique for measuring directly the bulk viscosity of water is proposed. By analyzing the relationship between the line width of Brillouin scattering and the shear and bulk viscosities, a relation of the bulk viscosity of water with the line width and frequency shift of Brillouin scattering is suggested, which is the basis for determining bulk viscosity experimentally. The experimental data of bulk viscosity of water at different temperatures were given. The testing error of this method is analyzed. Both of theory and experiments show that Brillouin scattering technique is a quick and accurate method for measuring bulk viscosity of water.