A ligator setup method for automatically tightening an elastic line and a self-tightening elastic line ligator. The self-tightening elastic line ligator comprises: at least one piece of an elastic line (30) disposed along an outer wall of an outer barrel (22) of the ligator. A front end of the elastic line (30) forms a size-adjustable loop loopingly disposed on an outer wall of a front end of an inner barrel (21). A distal end of the elastic line (30) connects to a line-retracting auto-connector (80) of the ligator. The other end of the line-retracting auto-connector (80) connects, via a compression spring (90), to a self-tightening trigger (100). When retracting the distal end of the elastic line (30), the self-tightening trigger (100) loosens the connection thereof to the compression spring (90). The line-retracting auto-connector (80) retracts and tightens the elastic line (30) by means of a recoiling force of the compression spring (90), rapidly reducing the size of the loop at the front end of the elastic line (30). The self-tightening elastic line ligator provides, via the compression spring (90), and to the line-retracting auto-connector, a recoiling force for retracting and tightening, automatically tightening the elastic line (30) so as to rapidly reduce the size of the loop at the front end of the elastic line (30) to a minimum or close to zero, thereby achieving a tighter and more secure ligature of a target tissue.
