The invention discloses a modified treatment method of castor oil used as a capacitor dipping agent, and belongs to the technical field of processing of capacitors. The modified treatment method specifically comprises the following steps: (1) precipitating and removing impurities; (2) cooling and dewaxing; (3) hydrating and degumming; and (4) distilling and purifying. Part of wax and gum of the castor oil are removed, then the castor oil is distilled and purified, the content of material components which affect performance of the dipping agent such as water, phospholipid and gossypol is reduced, the content of unsaturated fatty acid, particularly monounsaturated fatty acid, of the dipping agent is increased, coagulability, stability and insulativity of the dipping agent are improved well, then parameter performance such as a solidifying pint, a dielectric coefficient and dielectric loss of the castor oil as the dipping agent are improved, types and functions of capacitors of which the dipping agent is the castor oil are expanded, and the use value is high.