The invention belongs to technical field of electrochemical corrosion and provides a preparation method of a metallic tantalum substrate with the roughened surface. The preparation method comprises the following steps that an inert material is taken as a cathode, a metallic tantalum substrate is taken as an anode, an ethanol solution of tetraethyl ammonium chloride is taken as a electrolytic solution to conduct anodizationpitting corrosion treatment on the metallic tantalum substrate, the metallic tantalum substrate with the roughened surface is obtained, the distance between the cathode and the anode is 0.5-3.0 cm, the voltage of anodization pitting corrosion treatment is 8-20 V, and the time of the anodization pitting corrosion treatment is 5-40 min. Thepreparation method for themetallictantalum substrate with the roughened surface adopts electrochemical anodization treatment, in an organic system with chlorine ions, the chlorine ions penetrate through a passivation film on the tantalum surfaceunder the action of an electric field and corrode anode metallic tantalum and forms a large number of dense pitting corrosion pits on the surface of the metallic tantalum substrate, roughness of the tantalum substrate surface is increased, and the specific surface area of the tantalum substrate is also increased.