Abstract: For the problems of inconvenient acquisition of stemming materials and cumbersome operation of stemming process in tunnel blasting, a single component polyurethane stemming material was developed with the method of microencapsulation catalyst. The physical and mechanical properties of the material under different dosage of the catalyst and the mechanism of stemming were analyzed, and the field test of the stemming material was carried out. The results show that the optimum amount of catalyst coated by microcapsule is 0.64% (mass fraction),the surface drying time of the product is 250 s, and the curing time is 24 min, the compression pressure of 30 min is 0.22 MPa, the shear strength of 30 min is 0.16 MPa, the maximum reaction temperature is 20℃, the volume expansion rate is 30 times, and the oxygen index is 26%, which meets the requirements of stemming material. The polyurethane stemming material can better prolong the action time of the explosive gas, and the stemming time is 3-5 s per hole, 750 mL material can stemming 35-40 blast holes, and the relative cost is low; it has high reflectivity, the hole layout and stemming situation can be clearly grasped under the reflection of light.