Abstract: The reasons for large leakage current or the breaking down of the single tantalum anode block of capacitor are analyzed by using the scanning electron microscopy, and the main reason is that the local inclusions cause the abnormal growth of the oxide film, resulting in the discontinuity of the local tantalum oxide film on the surface of the particles, therefore, a large number of electrons pass through the leakage and even leads to the breakdown of the anode. The foreign body appearing in the tantalum anode block is the carbide inclusion of tantalum in the raw material of tantalum ingot, and the carbide inclusion of tantalum has high melting point and acid erosion resistance. In the subsequent treatment of the tantalum powder, the carbide inclusion of tantalum cannot be removed and remains in the tantalum powder. Backscatter electron imaging can be applied to tantalum sample detection.