An automatic traction device for a lower limb fracture osteosynthesis includes a chassis structure, a lower leg supporting structure and an upper leg supporting structure connected two by two. The automatic traction device further includes a tibia distal position adjusting device, for adjusting a position and an angle of a distal end of a tibia, on the lower leg supporting structure and close to the first end portion of the lower leg supporting structure; and a tibia proximal position adjusting device, for adjusting a position and an angle of a proximal end of a tibia, on the lower leg supporting structure and close to the second end portion of the lower leg supporting structure.