The invention relates to a single-hook double-tongue tightening earthing clamp provided with an n-shaped hook and an operating rod connector. The n-shaped hook is connected with the operating rod connector through a steering device. A double-tongue spring clamp plate is disposed in the n-shaped hook. Nuts are disposed on the outer side of one side of the n-shaped hook. The tail of the operating rod connector is hemispherical. A spring pin is mounted on the operating rod connector. The part of the clamp, in contact with a lead, is tightened by the single hook and double tongues, while the part of the clamp, in contact with an insulating operating rod, is angularly variable. The single-hook double-tongue tightening earthing clamp can be operated at all angles and is applicable to flexible use with variable angle devices; the tail of the operating rod connector is hemispherical, so that quick connection with an operating rod is facilitated. Therefore, the problem that the traditional earthing clamp has single operating angle is solved; fast, firm assembly of working site earth wires is ensured, quick connection with the operating rod is facilitated, and the single-hook double-tongue tightening earthing clamp is simple to use, safe and reliable with no need for preparation of additional other types of earthing clamps; the clamp can be assuredly mounted on wires or bus bars at any angle.