Abstract: In this paper, based on Protodyakonov’s pressure arch theory, the mechanical model of U-shaped steel support used for roadway support was proposed, the bearing capacity and reinforcement technology of the U-shaped steel support were studied, and the relation between the key reinforement position of the U-shaped steel support and the internal friction angle of the rock was analyzed. The research results showed that the sectional bending moment of the U-shaped steel support was mainly related to both the vertical and horizontal pressure of the surrounding rock, the sectional size of the roadway, the elasticity modulus, the gravity density of rock, the width of the caving arch, the compressive strength and solid coefficient of the rock and so on; the key reinforcement position of the U-shaped steel support was related to the internal friction angle of rock and the bottom width of the caving arch; the key reinforcement position of the arched beam of the U-shaped support was between 65° and 71°, and with the increase of the internal frriction angle of rock, the key reinflorcement position of the arched beam was far from the arched beam; the key reinforcement position of the U-shaped support leg was between 0 m and 1.01 m. and gradually shifted down with the increase of the internal friction angle of rock.