The invention provides an electromagnetic interference prevention device for a tong type ammeter. The electromagnetic interference prevention device comprises a metal shielding cover case capable of covering the tong type ammeter, wherein the metal shielding cover case comprises two halves of U-shaped hollow metal casings capable of covering jaws of the tong type ammeter from the two sides, a metal cap body covering the jaws of the tong type ammeter from the upper side is arranged above the two halves of the U-shaped hollow metal casing, in addition, a grounding wire connecting groove capable of ensuring the reliable grounding of the metal shielding casing is formed in the metal cap body, and a connecting part between the two halves of U-shaped hollow metal casings is provided with a rectangular gap used for connecting out a grounding lead-out wire of a transformer iron core. The electromagnetic interference prevention device has the characteristics that the structure is simple, the use is convenient and reliable, the electromagnetic interference resistance capability of the tong type ammeter can be effectively improved, the grounding current value of an iron core can be accurately measured, the charged detection level is improved, the safe and stable operation of an electric power system can be ensured, and the like.