The invention discloses the adjusting method of a compact infrared optical lens. The method comprises the following steps of (1) for all infrared lenses in a single infrared lens group, using space ring grinding and machining precision to ensure the interval and the coaxiality of all the infrared lenses; (2) using a visible light transmission material to make a single-piece tool lens, depicting across curve, and plating a semi-reflection semi-transparent film visible light band to replace the corresponding infrared lens group; (3) arranging trimming pads for interval adjustment and trimming pads for inclined angle and coaxial adjustment which are independent to each other on all lens barrels; (4) using a theodolite, standard flat glass, and a level meter to detect the inclined angles andthe coaxiality of a tooling lens and each plane mirror (5) adjusting the inclined angles and the coaxiality of the tooling lens and each plane mirror by the trimming pads; (6) using a laser range finder to detect the interval of each tooling lens, and reaching a design value through the trimming pads; and (7) using the infrared lens to replace the tooling lens to achieve the adjustment of a system.