Flame-retardant reed inorganic particleboard was prepared by hot-pressing with reed particles as a reinforcing material and using magnesite cement as an inorganic adhesive. The effects of inorganic sizing amount, density, and hot-pressing temperature and time on the properties of reed inorganic particleboard were investigated by orthogonal testing. Particleboard properties were tested and characterized by means of a universal mechanical testing machine, scanning electronic microscopy (SEM), X-ray diffraction (XRD), and cone calorimetry. The results showed that the mechanical properties of particleboard prepared under conditions of 60 percent sizing capacity, 100°C hot-pressing temperature, 15 minutes hot-pressing time, and 1.2 g/cm3 density were the best, reaching the national standard for cement particleboard. At 60 percent sizing, the characteristic peak value of inorganic adhesive hydrate crystal phase was the largest, the crystallization area dense and orderly, and the coating effect on shavings good; these attributes confirmed the trend of mechanical properties of reed shavings board increasing with sizing amount. Thus, the sizing amount had a significant influence on flame retardancy and smoke suppression performance of this particleboard. With an increased application amount, the heat release and total heat release rates of the particleboard and total smoke generation rate showed decreasing trends. Additionally, when the ignition time was delayed, the flame retardancy and smoke suppression performance of the particleboard was enhanced.