The invention discloses a hanger used for hoisting large-section steel truss girders and a hoisting method, and relates to the hoisting field of steel truss girders. The hanger is integrally symmetric along a longitudinal center line, comprises a first connecting assembly and a second connecting assembly which are connected with each other, wherein the first connecting assembly is used for connecting lifting lugs of the steel truss girder, and the second connecting assembly is used for connecting a lifting hook of a floating crane; the first connecting assembly comprises four first steel structural components, two limiting rods, two supporting rods and four moving parts, wherein the two limiting rods and the two supporting rods are used for connecting the four first steel structural components to form a quadrangle; the moving parts are fixedly connected with the supporting rods for moving the supporting rods in a length direction of the limiting rods; the second connecting assembly comprises four second steel structural components; and each first steel structural component is connected with one corresponding second steel structural component through a flexible connector. The hanger is adjustable in hanging point distance, can be used for hoisting large-section steel truss girders with different lifting lug distances, is strong in universality and is good in economical efficiency.