Abstract: This paper presents an established radical flow physical model, by means of which the produc tion process of oil well was simulated. By changing the viscosity and the flow velocity of the tested fluid, simulated the correlation of fluid viscosity, critical sand producing velocity and sand producing amount; by dis secting sand body, observing and describing the sand production profile, analyzed the sand producing mecha nism and laws of reservoir. It was found that the sand production from the unconsolidated sand reservoir did result from the variation of the effluent seepage field due to the change and damage of the rock texture.