The invention provides an anisotropic variable-modulus polyurethane-base composite damping material and a preparation method thereof. The composite damping material is prepared by curing a polyurethane base, magnetic particles and a crosslinking agent in a 40-60mT magnetic field, so that the magnetic particles generate directional arrangement in the curing process. The magnetic particles account for 20-100 wt% of the polyurethane base; and the mole ratio of the -NCO to the crosslinking agent -OH is 1:1.2. The damping material in a compressive state has the advantages of high dissipation factor, high storage modulus and great variation of modulus along with magnetic field intensity. Under the influence of 0-400mT, the storage modulus of the material under the frequency of 1Hz is increased from 2.2*10<6>Pa to 3.26*10<6>Pa. The composite damping material has the advantages of simple preparation technique and favorable damping capacity; the viscoelastic property can generate great variation under the action of the magnetic field; and the composite damping material can be used for designing various devices with controllable rigidity or damping, such as suspension systems, bushings, vibration absorbers and the like.