Because the heavy oil emulsion is opaque，it is impossible to intuitively understand the influence of sand particle on the stability of heavy oil emulsion. Scholars had detected the asphaltenes adsorbed on the surface of mineral particles by Fourier transform infrared spectroscopy. It was speculated that these particles destroyed the strength of oil/water interfacial film due to the adsorption of asphaltenes on the oil/water interfacial film and promoted the aggregation of water droplets，so as to realize the demulsification and stratification of heavy oil emulsion. However，this understanding couldn’t explain some phenomena in this experiment. In this paper，experiments such as bottle experiment，rheology test and wettability test were carried out，and the influence mechanism of quartz sand on the stability of heavy oil emulsion was studied. The results showed that when the particle size of sand was small and the particle size of water droplet was large，the phenomenon of water droplets completely wetting and wrapping the sand particles would occur. Furthermore，the proportion of water droplets wrapping sand particles increased，and the settlement speed accelerated. This was the main reason for the demulsification and stratification of heavy oil emulsion by sand，and this understanding was also verified by the sedimentation experiment of sand in white oil.