The invention relates to a preparation method of reclaimed rubber. Waste rubber is sequentially subjected to crushing, filtration separation, desulfurization and refinement, the reclaimed rubber is obtained, the desulfurization step specifically comprises processes as follows: 100 parts by weight of waste rubber obtained after filtration separation, 10-15 parts by weight of a rosin softening agent, 2-3 parts by weight of a dipentene reclaiming activator, 2-3 parts by weight of a triethylene tetramine softening agent and 5-10 parts by weight of a triethanolamine reclaiming activator are mixed,desulfurization treatment is performed under the pressure of 5-10 MPa and at the temperature of 130-170 DEG C for 40-50 min, and then, the refinement step is performed. The preparation method of the reclaimed rubber has the advantage that the tensile strength of the reclaimed rubber can be effectively improved to 15-19 MPa.