In order to evaluate the effect of dispersant on the stability of heavy oil accurately，the improvement effects of 5 kinds of dispersants on the stability of asphaltenes or heavy oils of Gudao and Guantao were studied. The dispersants included sulfonic acid anionic dispersant AA，Span series dispersant NA1，oleic acid，lauric acid and palmitic acid. The results showed that the dispersants had certain improvement effects on the stability of asphaltenes or heavy oils. Among them，AA and NA1 could significantly reduce the degree of asphaltene aggregation，and had the strongest stable dispersion effect on asphaltenes. The improvement effect on the asphaltene was generally better than that on the overall stability of the corresponding heavy oil. The improvement effect of dispersant on asphaltene stability increased with increasing concentration of dispersant. Asphaltene completely exposed in the system，and it was easy to interact with dispersant. The improvement effect of dispersant on the overall stability of heavy oil increased first and then decreased with increasing dosage of dispersant. There was an optimum value for the amount of dispersant. The improvement of asphaltene stability had an important impact on the overall stability of heavy oil，but that of heavy oil stability was also affected by resin，aromatics and saturation，and so on.