The invention relates to a drilling tool adapter, which comprises a connector, a small core tube and a core tube, wherein one end of the small core tube is positioned in the inner part at one end of the core tube, the other end of the small core tube is provided with an inner rubber spring and an outer rubber spring, the small core tube and the core tube are both arranged in the connector, a clamping key is arranged between the connector and the core tube, the top upper end of the connector is provided with a rear pressing cover which is fixed on the connector through a fastening piece, and one end of the core tube, which is positioned at the outer part of the connector is provided with a spring. In the invention, when the drilling tool adapter is rotated tightly with a drilling tool, larger impact force of the drilling tool adapter with motive power can be acted on the drilling tool, the impact to the drilling tool can be effectively reduced through a rubber spring assembly, and thus the threads of the drilling tool and the connector can be protected; and when the drilling tool adapter and the drilling tool are unscrewed to separate, the unscrewing and the separating can be processed at the same time depending on the acting force of the spring, thus the threads are protected, and the threads of the drilling tool are prevented from being drilled by the drilling tool adapter on site. According to the drilling tool adapter, the protection for the drilling tool during an idle motion is effectively realized, and the drilling tool is prevented from being damaged when shackling.