The invention discloses a system for joint production of carbide, lime nitrogen and carbon black and a method. The system comprises a carbide granulation tower, a nitridation furnace, a first cyclone separator and a powder separating device, wherein a heat exchange zone and a gas distribution zone are defined in the carbide granulation tower from top to bottom, the heat exchange zone is provided with a rotary granulating machine, the rotary granulating machine comprises a rotating disc and a rotating shaft arranged at the lower end of the rotating disc, a carbon dioxide distribution plate is arranged below the rotating disc, a carbide liquid inlet and a heat-exchanged carbon dioxide outlet are formed in the upper end of the heat exchange zone, and a second carbon dioxide inlet and a carbide granule outlet are formed in the gas distribution zone; a nitridation reaction space and a gas distribution space are defined in the nitridation furnace from top to bottom, the nitridation reaction space is provided with a carbide granule inlet and a nitridated gas outlet, and a nitrogen gas inlet and a granular lime nitrogen outlet are formed in the gas distribution space; the first cyclone separator is provided with a gas mixture inlet, a first dedusted gas outlet and a lime nitrogen powder and carbon black containing dust outlet; and the powder separating device is provided with a dust mixture inlet, a lime nitrogen powder outlet and a carbon black outlet.