An instrument for implementing a completely laparoscopic staged hepatectomy including a liver-around band made of flexible materials of which one end is a free end, and the other end is provided with a through hole; wherein the free end is configured to pass through the through hole to form a loop that can tighten the liver; and wherein the side of the liver-around band facing away from the liver is defined as the outer side; wherein the outer side of the liver-around band is provided with first ratchet teeth; characterised in that the instrument further includes an abdominal wall catheter and a pressure control device, wherein the free end of the liver-around band passes through the through hole, the abdominal wall catheter, and the pressure control device in sequence, wherein the abdominal wall catheter is configured to pass through the patient's abdominal wall; the pressure control device includes a first sleeve and a buckle, wherein the direction of the central axis of the first sleeve is taken as the longitudinal direction, and wherein the first sleeve is provided with a longitudinal first inner hole and a longitudinal guide groove for passing through/inserting the buckle, and wherein the buckle is arranged in the longitudinal first inner hole and the longitudinal guide groove of the first sleeve and can move longitudinally along the longitudinal first inner hole and the longitudinal guide groove; the buckle is provided with a second inner hole and a second ratchet tooth extending into the second inner hole; wherein the liver-around band passes through the second inner hole of the buckle, so that the first ratchet teeth mesh with the second ratchet tooth; the second ratchet tooth allows the first ratchet teeth to slide in the positive direction of tightening the loop while preventing the first ratchet teeth from sliding in the reverse direction; a spring arranged in the longitudinal direction is installed between the buckle and the first sleeve, wherein the first sleeve, the buckle and the spring are configured to set physical parameters in accordance with the requirements for a tightening force of the liver during an operation; the buckle is provided with a vernier for marking the tightness of the liver-around band, and a scale of the vernier is provided on the first sleeve. wherein the outer side of the liver-around band is provided with first ratchet teeth; characterised in that the instrument further includes an abdominal wall catheter and a pressure control device, wherein the free end of the liver-around band passes through the through hole, the abdominal wall catheter, and the pressure control device in sequence, wherein the abdominal wall catheter is configured to pass through the patient's abdominal wall; the pressure control device includes a first sleeve and a buckle, wherein the direction of the central axis of the first sleeve is taken as the longitudinal direction, and wherein the first sleeve is provided with a longitudinal first inner hole and a longitudinal guide groove for passing through/inserting the buckle, and wherein the buckle is arranged in the longitudinal first inner hole and the longitudinal guide groove of the first sleeve and can move longitudinally along the longitudinal first inner hole and the longitudinal guide groove; the buckle is provided with a second inner hole and a second ratchet tooth extending into the second inner hole; wherein the liver-around band passes through the second inner hole of the buckle, so that the first ratchet teeth mesh with the second ratchet tooth; the second ratchet tooth allows the first ratchet teeth to slide in the positive direction of tightening the loop while preventing the first ratchet teeth from sliding in the reverse direction; a spring arranged in the longitudinal direction is installed between the buckle and the first sleeve, wherein the first sleeve, the buckle and the spring are configured to set physical parameters in accordance with the requirements for a tightening force of the liver during an operation; the buckle is provided with a vernier for marking the tightness of the liver-around band, and a scale of the vernier is provided on the first sleeve.