The invention discloses an environment-friendly weld joint sealant, and a preparation method thereof. The environment-friendly weld joint sealant is prepared from, by weight, 15 to 25 parts of DINCH,5 to 10 parts of TBC, 12 to 15 parts of PVC paste resin, 2 to 5 parts of hydroxyl-modified vinyl resin copolymers, 1 to 2 parts of an adhesion promoter, 3 to 5 parts of a diluents, 20 to 30 parts of ananometer filling material, 15 to 25 parts of heavy calcium carbonate, 1 to 5 parts of a moisture absorbing agent, 0 to 1 part of a thixotropic agent, 0.8 to 2.5 parts of a stabilizing agent. According to the preparation method, DINCH and TBC plasticizers are adopted at an appropriate ratio, two different PVC main materials including PVC paste resin and hydroxyl-modified vinyl resin copolymers are adopted, and the other ingredients are selected to prepare the environment-friendly weld joint sealant; the environment-friendly weld joint sealant contains no o-benzene compound, is used for coating vehicle bodies, and possesses water resistance, sealing performance, and shockproof effect after roasting and heating plasticizing together with vehicle bodies.