A new method for measuring fluid viscosity proposed here is based on the dynamic light scattering (DLS) technique. The scattering light from the Brownian particles suspended in liquid was detected by photomultiplier through the collection lens and aperture with polarizer. The time-averaged autocorrelation function of photon number of scattering light from the particles gives the diffusion coefficient of Brownian particle. The diffusion coefficient is related to the fluid viscosity and the particle radius according to the Einstein-Stokes relation. Hence, if the radius of the particles is known, it is possible to obtain the relation between the fluid shear stress and the shear rate from the diffusion coefficient of Brownian particle and then to measure the viscosity of the fluid with DLS. The DLS technique allows for the viscosity of fluids in stationary condition to be measured without using a moving object in the fluid. We have applied this method to perform a simple measurement of the viscosity of fluid at high pressure by using special high-pressure equipment. We have measured the viscosity of some kinds of liquids at the pressure up to 400 MPa. The results show that the viscosity at high pressure might be correlated by the Tait-type equation.