Abstract:The lower layer of magnesium crystal plate reinforced concrete composite floor is a prefabricated new fire-resistant magnesium crystal plate, and the upper layer is cast-in-situ reinforced concrete plate. In order to study the fire resistance of magnesium crystal plate reinforced concrete composite slab under different load ratios, three composite slab specimens were tested subjected to ISO-834 standard temperature rise, and the fire time temperature curve and mid span fire time deflection curve at different positions of the composite slab were obtained. The test results show that the composite slab has good fire resistance and the fire resistance limit can reach more than 1.5 hours. The fire resistance of the specimens was analyzed by using the finite element software ABAQUS, and the effects of load ratio, magnesium crystal plate thickness, protective layer thickness, reinforcement and concrete strength on the fire resistance limit were investigated. The analysis shows that the load ratio and the thickness of magnesium crystal plate have a great influence on the fire resistance limit. According to the test and finite element analysis results, the calculation method of fire resistance limit of composite slab is put forward, which can provide reference for fire protection design of composite slab.