The invention discloses a thermosetting resin composition and a preparation method and a using method thereof. The composition comprises a substance A and a substance B in a mass ratio of 100:1-100, wherein the substance B is a curing agent; the substance A consists of the following components in part by weight: 100 parts of thermosetting resin, 10 to 600 parts of filler, 1 to 10 parts of pigment, 0 to 100 parts of activated or non-activated thinner, 0 to 5 parts of ultraviolet absorbent, 0 to 5 parts of antioxidant, 0 to 2 parts of antifoaming agent and 0 to 5 parts of coupling agent; all the components of the substance A are stirred at the temperature of between 5 and 180 DEG C and the stirring rate of 10 to 3,000 revolutions per minute and mixed in vacuum for 0.1 to 10 hours and the substance A is obtained by packaging the mixture; and the substance B is obtained by packaging the curing agent. The composition is used as an elastic filling connection material among ballastless trackslabs of a railway and has high adhesion, ultraviolet irradiation resistance, wet and heat ageing resistance and chemical corrosion resistance, and certain elasticity and mechanical strength.