The invention discloses a method for adjusting and positioning a thermal imager for use in thermal imaging monitoring of a liquefied natural gas (LNG) storage tank. The method comprises the following steps: (1) determining the mounting distance of the thermal imager according to the field angle of the thermal imager; (2) setting the mounting height of the thermal imager according to site requirements; (3) arranging a point heat source at a position accounting for a half of the height of the storage tank, and starting the infrared thermal imager, wherein the thermograph shooting center of the infrared thermal imager is coincided with the set point heat source; (4) converting the coordinate of an upper height boundary point and a lower height boundary point on the middle axis of a thermograph shot by the infrared thermal imager along a vertical direction into height coordinates on the outer wall of the storage tank; (5) keeping the inclination angle of the infrared thermal imager invariable, and moving the infrared thermal imager by a preset distance along the vertical direction to allow the thermal infrared image to shoot an image in the height direction of the storage tank at one time. By adopting the method, all heights of LNG storage tanks can be detected, and the temperature field change of the outer wall of the storage tank is found in time.