The invention discloses powdery polystyrene-beta-random-copolymerization conjugated diene/divinylbenzene rubber, and a preparation method and application thereof. The rubber is formed through styrene homopolymerization block and conjugated diene and divinylbenzene random copolymerization block. The preparation method of the rubber comprises firstly adding a styrene monomer into an anionic polymer system containing anisole, and performing homopolymerization; after homopolymerization is finished, adding mixed monomers of conjugated diene and divinylbenzene, and performing random copolymerization, so as to obtain a rubber solution; and performing agglomeration on the rubber solution to remove solvents, so as to obtain the rubber. The preparation method is simple and low in cost, the prepared rubber is applicable to self-adhesive type modified asphalt waterproof coiled materials with excellent performance, and the like, and the prepared rubber shows the characteristics of resistance to low temperature, relatively high ductility, and relatively high peeling strength and heat resistance.