The invention discloses a prefabricated frame column lightning-proof down-lead connecting device. The device comprises a connecting device body which comprises a connecting component and a first connecting rod, a second connecting rod, a first release rod and a second release rod which are installed on the connecting component; the end, away from the connecting component, of the first connecting rod is installed on a first upper main reinforcement, the end, away from the connecting component, of the second connecting rod is installed on a second upper main reinforcement, the end, away from theconnecting component, of the first release rod is installed on a first lower main reinforcement, and the end, away from the connecting component, of the second release rod is installed on a second lower main reinforcement. By means of the connecting device, a main reinforcement of a prefabricated frame column can also serve as a lightning-proof down-lead, the problem that when an existing metal wire special for the external wall exposed laying serves as the lightning-proof down-lead, potential safety hazards are likely to be generated, and maintenance is needed is avoided, and the productionand manufacturing cost is effectively lowered. The invention further discloses a method for installing the prefabricated frame column lightning-proof down-lead connecting device.