The invention discloses a prefabricated assembling U-shaped channel structure which comprises multiple U-shaped components sequentially assembled to form the U-shaped channel structure. The U-shaped components comprise prefabricated bottom plate components and prefabricated side wall components; splicing steps are arranged on the longitudinal side surfaces of the prefabricated bottom plate components and the prefabricated side wall components; pre-embedded steel slabs are arranged on the step surfaces of the splicing steps; the splicing steps of each two adjacent U-shaped components are spliced to form a groove; the pre-embedded steel slabs of each two adjacent U-shaped components are connected through a welding steel plate; two sides of each welding steel plate are welded to the surface of each adjacent pre-embedded steel slab; and concretes are poured in the grooves. The invention further discloses a method for installing the U-shaped channel structure. The method comprises the stepsof hoisting and assembling the prefabricated bottom plate components, hoisting and assembling the prefabricated side wall components, pouring the concretes, sequentially hoisting and assembling the next section, and the like. The prefabricated assembling U-shaped channel structure provided by the invention has the advantages of simple structure, convenience in installing, fast construction speed,less influence on the periphery, good stressing and waterproof effects, consistency of sections, high stability and the like.