The invention discloses a perforating tool for a spline hole on the surface of an oil tank. The perforating tool comprises a cutter body and a base, wherein cutters which can turn relative to the cutter body and have the spline notch cross section shape are arranged at the two vertical sides of the lower end of the cutter body; a position limiting hole through which the cutter body and the cuttersvertically penetrate is formed in the middle of the base; the position limiting hole has the spline notch cross section shape; and a connecting rod assembly used for driving the cutter body to upwards move is detachably arranged on the upper end of the cutter body, so that the perforation of the spine hole on the surface of the oil tank between the cutter and the position limiting hole is realized. The perforating tool for the spline hole on the surface of the oil tank has the advantages that through the joint action of the cutter with the spline notch cross section shape and the position limiting hole with the spline notch cross section shape, the perforation of the spline hole on the oil tank can be realized; cut impurities enter the position limiting hole along with the cutters, so that the impurities are prevented from falling into the oil tank during the perforation; the perforating process is fast and convenient; and the realization is easy.