The invention relates to a folding safety gate, and belongs to the field of an antitheft door. A main door and a sub door of the folding safety gate are connected through hinges; a transverse lock cavity is formed in each of the main door and the sub door; a clamp seat, a pin seat and a transverse clamp pin are arranged in each transverse lock cavity; a pin hole is formed in each of the pin seat and the transverse clamp pin; a lock cavity cover is fixed outside the transverse lock cavity; an antitheft lock arranged on the lock cavity cover is matched with the inner end part of the transverse lock cavity formed in the sub door, so that the transverse lock cavity can be closed or opened; the lock cavity cover arranged outside the locked transverse lock cavity can limit the transverse clamp pin not to move in the clamp seat; and further, the goal of locking the main door and the sub door on the same plane is realized. The folding safety gate has the advantages that the structure is simple and compact; the manufacturing and the use are convenient; during the door opening, the opening degree is small; the folding safety gate is suitable to be installed and used in a position for replacing a double door; and the industrialized market prospect is good.