An asphalt regenerant is mainly prepared from 40-60 parts of a regeneration component, 15-30 parts of nano organic montmorillonite modified asphalt, 15-30 parts of a plasticizer and 1-5 parts of a penetrant; the regeneration component is mixed oil mainly formed by mixing light oil and heavy oil in proportion. The preparation method of the asphalt regenerant comprises steps as follows: a reaction kettle is preheated and heated, the regeneration component is added to the reaction kettle, the nano organic montmorillonite modified asphalt is added in parts by mass after stirring, the temperature is controlled within 130-160 DEG C, the temperature is decreased to 80-120 DEG C after stirring, the penetrant and the plasticizer are added, the mixture is stirred continuously, and the asphalt regenerant is obtained after cooling. During usage, the reaction kettle is preheated, waste aged asphalt is added, the temperature is decreased gradually after quick stirring, then a certain proportion of asphalt regenerant is added, and regenerated asphalt is obtained after quick stirring. The product performance is good, the cost is low, and the technology is simple, controllable and environment-friendly.