Abstract: A solid waste base ternary cementitious system composed of slag powder, fly ash and desulphurized gypsum was combined with cement, polystyrene particles and blowing agent to prepare monolithic composite wall panels of prefabricated steel structure residential buildings through the orthogonal test ratio scheme. The performance test was conducted to test the compressive strength, dry volume density, thermal conductivity and water absorption of the prepared materials were tested at different levels of factor combinations, with the compressive strength and dry volume density as the main objectives, the composite wallboard material mix ratio was selected. Based on the optimal mix ratio, two kinds of steel bars and GFRP bars were selected to make flexural specimens of wall panels with and without window holes for bending performance tests. The bending performance of the materials was investigated based on parameters such as the cracking load, ultimate failure load, load-strain curve of concrete, load-strain curve and load-deformation curve of in-plate reinforcement. The results show that the optimal material mix is water-binder ratio 0.4, terpolymer cementation ratio 1∶1∶3, replacement cement ratio 50%, polystyrene particle volume content 35%. At this time, the wall panel material has good mechanical, light weight and thermal insulation properties. The 28 d compressive strength is 11.12 MPa, the dry bulk density is 973 kg/m³, the thermal conductivity is 0.187 (W/(m·K), and the water absorption is 10.06%. The bending resistance of the wall panel material is good, and the cracking load and ultimate failure load of reinforced wall panels are greater than that of GFRP wall panels. The cracking load and ultimate failure load of reinforced wall panels are affected by opening holes.