Abstract: Low-hydrated zinc borate（2ZnO·3B₂O₃·3H₂O） was prepared by microwave hydrothermal method with ZnO and H₃BO₃ as raw materials.The structure，properties，and morphology of the prepared zinc borate were characterized by means of X-ray powder diffraction（XRD），thermogravimetric（TG-DTA），and scanning electron microscopy（SEM） etc..At the same time，different factors affecting the microwave hydrothermal process were discussed.The suitable synthesis conditions were confirmed through optimized experiments.Experimental results showed that the XRD spectrum of the obtained product was in agreement with the standard spectrum of 2ZnO·3B₂O₃·3H₂O，the dehydration temperature of the sample was above 360 ℃，and the grain size was at 1~2 μm after aging.

Key words: inorganic flame retardant, zinc borate, microwave hydrothermal method