Flame retardants are very important for our life.These materials are added to flameable items to increase their stability against ignition.Zinc borates are an important class of flame retardants.In this thesis, zinc borate has been prepared from two different precursors including [Zn(en) 3 ](BPh 4 ) 2 and H 3 BO 3 /ZnO.In the first method, tris(ethylenediamine) zinc(II) tetra phenyl borate [Zn(en) 3 ](BPh 4 ) 2 complex was prepared by reaction of ZnCl 2 with en ligand in the presence of NaBPh 4 in water.The prepared Zn(II) complex was investigated under there operation, hydrothermal, solvothermal and calcination to obtain zinc borate. Only in the calcination operation, the final product at the calcination temperature of 650 ?C is pure zinc borate. The products of other operations were impore.In the second method, a mixture of H 3 BO 3 /ZnO with a mole ratio of 6:2 was reacted under the hydrothermal operation at 200 ?C.In this method, the final product was zinc borate.The prepared zinc borates have been characterized by FT-IR, XRD, SEM and TGA.In addition, the application of the prepared zinc borates as a flame retardant was tested in poly(acrylonitrile) at different weight ratios.The results show that the addition of zinc borate to (PAN) can increase its stability against ignition and the combustion process imidiately terminated when the sample removed from the flame.Therefore, the prepared zinc borates are good candidates for use as flame retardants.