A self-tightening elastic line ligator, comprising a body , a barrel and at least one elastic line , wherein the barrel comprises an inner barrel and an outer barrel , the elastic line is disposed along an outer wall of the outer barrel of the ligator, a front end of the elastic line form a size-adjustable loop loopingly disposed on an outer wall of a front end of the inner barrel , the ligator further comprises an elastic line automatic tensioning mechanism, wherein the elastic line automatic tensioning mechanism comprises: a line-retracting auto-connector , wherein a tail end of the elastic line is connected with the line-retracting auto-connector , a compression spring of which one end abuts the body and the other end abuts a free end of the line-retracting auto-connector , and a self-tightening trigger , which can keep abutting the free end of the line-retracting auto-connector with a resilient force, to keep the compression spring being compressed; wherein the elastic line automatic tensioning mechanism is configured such that when the tail end of the elastic line needs to be retracted, the self-tightening trigger can be pressed to release an abutment to the free end of the line-retracting auto-connector , and thus releases an abutment to the compression spring , and the line-retracting auto-connector is rebounded backward to tighten backward the elastic line under an action of a resilient force of the compression spring , thereby rapidly reducing a size of the loop at the front end of the elastic line . the barrel comprises an inner barrel and an outer barrel , the elastic line is disposed along an outer wall of the outer barrel of the ligator, a front end of the elastic line form a size-adjustable loop loopingly disposed on an outer wall of a front end of the inner barrel , the ligator further comprises an elastic line automatic tensioning mechanism, wherein the elastic line automatic tensioning mechanism comprises: a line-retracting auto-connector , wherein a tail end of the elastic line is connected with the line-retracting auto-connector , a compression spring of which one end abuts the body and the other end abuts a free end of the line-retracting auto-connector , and a self-tightening trigger , which can keep abutting the free end of the line-retracting auto-connector with a resilient force, to keep the compression spring being compressed; wherein the elastic line automatic tensioning mechanism is configured such that when the tail end of the elastic line needs to be retracted, the self-tightening trigger can be pressed to release an abutment to the free end of the line-retracting auto-connector , and thus releases an abutment to the compression spring , and the line-retracting auto-connector is rebounded backward to tighten backward the elastic line under an action of a resilient force of the compression spring , thereby rapidly reducing a size of the loop at the front end of the elastic line . a line-retracting auto-connector , wherein a tail end of the elastic line is connected with the line-retracting auto-connector , a compression spring of which one end abuts the body and the other end abuts a free end of the line-retracting auto-connector , and a self-tightening trigger , which can keep abutting the free end of the line-retracting auto-connector with a resilient force, to keep the compression spring being compressed; wherein the elastic line automatic tensioning mechanism is configured such that when the tail end of the elastic line needs to be retracted, the self-tightening trigger can be pressed to release an abutment to the free end of the line-retracting auto-connector , and thus releases an abutment to the compression spring , and the line-retracting auto-connector is rebounded backward to tighten backward the elastic line under an action of a resilient force of the compression spring , thereby rapidly reducing a size of the loop at the front end of the elastic line . <EOS>