Abstract: Aiming at a large span half-steel-concrete (HSC) composite beam in the composited roof in High Temperature Reactor Pebble-bed Module （HTR-PM） Demonstration Project, a specimen with scaled-down size was investigated by the static load test. The deflection, strain and fracture development of the specimen in the loading process were analyzed and the mechanical characteristics and failure pattern of such components were studied. The finite element model of the HSC composite beam specimen was established and analyzed. The results show that under the ultimate load, the maximum deflection at the middle of the specimen beam obtained from the simulation results are basically consistent with the test results, and the tiny cracks first appear on the concrete surface of the lower part of the side web of the beam. The steel plate and concrete in such type of structure can effectively form as composite cross-section working together and the HSC composite beam has good load carrying capacity and ductility. These conclusions can serve as a preliminary design reference for the large span HSC composite beam in NPP.