Abstract: Demulsification of emulsified crude oil of acidizing wells is always a technical difficult problem in Tahe oilfield. This work investigated the demulsification of two kinds of Tahe emulsified crude oils by light scattering method and electrostatic field method, respectively, and then analyzed the main factors affecting the demulsification of emulsified oil from three aspects of residual chemicals, solid particles, resins and asphaltenes. The results show that the guar gum in fracturing fluid and the hydrochloric acid in acidizing fluid are harmful to demulsification; the existing solid particle composed of lipophilic compounds of iron and sulfur promotes the stabilization of W/O fluids; the asphaltene aggregate having worse solubility in acid oil is easy to form a stable asphaltene film. The synergistic effect of these three factors together increases the difficulty on demulsification of Tahe emulsified oils.