One of the most promising methods in order to mitigate asphaltene precipitation is to use asphaltene dispersants. In this study, the effect of two dispersants of toluene and dodecylbenzene sulfonic acid on asphaltene precipitation of a dead and a live oil sample has been investigated. Investigations on dead oil were conducted using IP143 standard test and for studying live oil in the presence of asphaltene dispersants high pressure microscopy was used. The obtained pictures from high pressure microscopy were analyzed using a picture analysis software. According to the results, this dispersants in dead oil create an optimum point for asphaltene precipitation. In live oil, this dispersants reduce asphaltene precipitation, moreover, for dodecylbenzene sulfonic acid, the reduction in asphaltene precipitation reaches down to 70 percent. Also, it was observed that in the effect of injection of these dispersants, the average size of asphaltene flocculation has reduced, which this reduction was much more for dodecylbenzene sulfonic acid in comparison with toluene.