The invention discloses polyurethane-modified daub for leaking stoppage. The daub comprises a component A, a component B and a component C in the total weight part ratio being 100: (40-60): (5-20), wherein the component A is prepared from polyurethane-modified epoxide resin, mica powder Al2O3 and diethylene glycol; the component B is prepared from diethylenetriamine, a single epoxy compound, a DMP (dimethyl phthalate)-30 catalyst and colloidal graphite; the component C is prepared from thiourea or a thiourea derivative, CaO and/or Ca(OH)2 and 8-hydroxyquinoline. Compared with the prior art, the provided polyurethane-modified daub for leaking stoppage has good toughness, can effectively prevent propagation of cracks in a pipe, guarantees the repairing effect and can stop leakage at the temperature and under pressure, cracks of equipment can be prevented through coating in advance, the curing speed of the daub in winter is high, the material is environment-friendly, no side effects and odors are produced, and the operation safety is good.