To solve the method of measuring the viscosity of related substance at high pressures and high temperatures, Sakharov has proposed an experimental method of small disturbance in shock wave. However, the quantitative relation between the disturbance amplitude damping and viscosity in Sakharov flow field has not been given by theory. In this paper, the propagation of complex flow in Al, the development of relative disturbance amplitude on sinusoidal shock front, and the effect of viscosity on it are studied, and the relation between the relative distance of zero-point on the disturbance amplitude damping curve and viscosity is given. Compared with Zaidel’s uniform flow model and Millers’ nonuniform flow model, our Sakharov flow is close to real experiment. From our numerical analysis method, Sakharov small disturbance experiment can give a credible viscosity coefficient. We analyze the experimental data of Mineev again, and find the effective viscosity coefficient of Al at shock pressure 31 GPa and strain rate 2×106 s-1 should be modified by 1100 Pa·s, which is half of the former analytic result.