A chain intelligent pre-tensioning and chain length detection device, comprising a rack, a work platform, a pre-tensioning power device, a measuring power device, a length measuring device and a console; wherein the console is located beside the rack, and the console is configured to receive information of the length measuring device to adjust and control the pre-tensioning power device, the work platform is fixed on top of the rack; the work platform is provided with two large guide rails in parallel, and a first elongated through hole is disposed between the two large guide rails, the pre-tensioning power device comprises a servo system, a decelerator, a belt, a second screw, a second nut, a first large pallet, a first fixing block, a pre-tensioning force sensor, a second fixing block, a second large pallet and a fourth fixing block, bottoms of the first large pallet and the second large pallet are slidably disposed on the two large guide rails through a slider, one end of the first large pallet is fixed with the first fixing block, one end of the second large pallet adjacent to the first large pallet is fixed with the second fixing block, one end of the pre-tensioning force sensor is fixed to the second fixing block, and the other end of the pre-tensioning force sensor is elastically connected to the first fixing block, the servo system, the decelerator and the second screw are disposed at bottom of the work platform through a mounting plate, the decelerator is configured to drive the second screw through the belt, and the second screw is further provided with the second nut, the second nut is fixed with bottom of the first large pallet after penetrating through the first elongated through hole, the first large pallet can move linearly, in use, along the two large guide rails under the driving of the servo system; the second large pallet is provided with two small guide rails in parallel, and a second elongated through hole is further provided between the two small guide rails, the measuring power device comprises a stepper motor, a first screw, a first nut, a first small pallet, a measuring force sensor, a third fixing block, a second small pallet and a fourth fixing block, wherein bottoms of the first small pallet and the second small pallet are slidably disposed on the two small guide rails, one end of the first small pallet is provided with a protrusion protruded upward, one end of the second small pallet adjacent to the first small pallet is fixed with a third fixing block, and the other end of the second small pallet is fixed with a clamp, two ends of the measuring force sensor are respectively fixed to the protrusion and the third fixing block, the stepper motor and the first screw are disposed at bottom of the second large pallet, and the first screw is further provided with the first nut, the first nut is fixed to bottom of the first small pallet after penetrating through the second elongated through hole, the first small pallet can move linearly, in use, along the two small guide rails under the driving of the stepper motor; the length measuring device comprises a grating ruler, a straight guide rail and an automatic measuring head disposed on one side of the work platform, a plurality of clamp fixing blocks are further distributed at equal distance on the work platform, the plurality of clamp fixing blocks are fixed on the rack, upper surfaces of the plurality of clamp fixing blocks are lower than the work platform and covered by a cover to maintain a level of the work platform, the corresponding clamp fixing block can be selected, in use, according to a specific chain length to fix the clamp.