Abstract: To study sand migration issues in the production of the heavy oil reservoir of unconsolidated sandstone,a series of laboratory experiments were performed according to the solid-liquid two-phase flow theory and the experimental fluid mechanics theory.Those experiments included setting of round particles and sand in high viscous fluid,and mixed viscosity variation pattern of heavy oil with different sand concentration.Based on experiment results,we established resistance coefficient model and mixed viscosity model under different grain size,which revealed the mixed viscosity of high viscosity oil had a critical sand volume fraction.It demonstrated that the mixed viscosity is the lowest when the sand volume fraction is 0.1%.Based on this model,sand transport model in high viscous Newtonian fluid was set up,which reveals particle migration pattern in high viscosity medium,and lays foundation for the study on sand carrying flow pattern of heavy oil.