The combined AGV chain tensioning device comprises a tensioning piece, a trigger device and a telescopic reciprocating mechanism which are connected in sequence, the trigger device comprises a fixed block and a sliding block, a first cavity and a second cavity which are communicated through a first through groove are formed in the fixed block, a limiting groove is formed in the second cavity, and the telescopic reciprocating mechanism is arranged in the limiting groove. A second through groove communicated with the limiting groove is formed in the fixing block, the sliding block is limited in the second cavity and slides in the extending direction of the second cavity, a triggering protrusion and a connecting rod are arranged at the two ends of the sliding block respectively, the triggering protrusion penetrates through the first through groove to be located in the first cavity, and a tightness detection switch is arranged in the first cavity; the connecting rod sequentially penetrates through the limiting groove and the through groove to be located on the outer side of the fixing block, the connecting rod is sleeved with a reset spring, one end of the reset spring abuts against the outer wall of the sliding block, the other end of the reset spring abuts against the groove wall of the limiting groove, the tensioning piece is fixed to the connecting rod, and the telescopic end of the telescopic reciprocating mechanism is connected with the fixing block.