The present invention relates to the technical field of oleanolic acid drugs and provides a drug sustained release agent based on oleanolic acid and a preparation method thereof. The drug sustained release agent based on the oleanolic acid is applied to drugs with the oleanolic acid as a main drug component and is prepared from the components including a drug carrier, a hydrophilic gel material, a erodible matrix material and an insoluble matrix material, wherein the drug carrier is β-cyclodextrin-chitosan composites, wherein the oleanolic acid is from a plant raw material, and a host-guest inclusion complex is composed of the main drug component and the drug carrier according to the mass ratio of 0.1:0.1-0.1:5. A preparation method comprises the following steps: preparing the inclusion complex, mixing auxiliaries, carrying out compression moulding and the like. The drug sustained release agent based on oleanolic acid has the characteristics of stable drug concentration, high biological activity, good drug solubility and long acting effect.
