Disclosed is a portable grounding down lead reset mounting apparatus used for being matched with a lifting mechanism to reset and mount the grounding down lead to a tower angle iron. The portable grounding down lead reset mounting apparatus comprises a locking mechanism for tightly holding the tower angle iron detachably, wherein the locking mechanism comprises a main beam used for fixing the lifting mechanism, a first tightening assembly which is arranged at one end of the main beam and can buckle one side edge of the tower angle iron, and a second tightening assembly which is arranged at the other end of the main beam and can buckle the other side edge of the tower angle iron; the second tightening assembly comprises a tightening seat which can be hinged at the other end of the main beam in a swinging manner in a locking position and a releasing position, a pull rod which can be hinged on the tightening seat in a swinging manner, and a second buckling part which is arranged on the pull rod and can buckle the other side edge of the tower angle iron; and it is set that when the tightening seat swings from the releasing position to the locking position, the pull rod can be driven to retract backwardly so as to enable the second buckling part to tightly buckle the edge of the tower angle iron.