The invention relates to the field of materials used for road engineering test detection, and particularly provides a sealing material used for bituminous pavement in-situ permeability tests, a preparing method thereof and a supporting construction tool. The sealing material is prepared by mixing calcium carbonate, base oil, a thickening agent, kaolin, silica, an antibacterial agent, and the like, and is characterized by environment protection, high operationality, good sealing performance, easy storage, no hand sticking, easy recovery, capability of being reutilized, no pollution to bituminous pavements, and the like. When the sealing material is used with the supporting construction tool, the testing efficiency can be greatly increased. The sealing material has good practicality and popularization value.