Abstract: <FONT face=Verdana>Precursor,magnesium borate hydroxide whiskers \[MgBO2(OH)\] with aspect ratio of 30~90 were prepared at 190 ℃ for 10 h by using hydrothermal method with magnesium chloride hexahydrate and boric acid as raw materials.Magnesium borate (Mg2B2O5) whiskers&nbsp; with aspect ratio of 50~80 and homogeneous dimension were then obtained by calcining of the precursor at 700 ℃ for 3 h followed by structure rearrangement and phase inversion.XRD,SEM and TG etc.were used to characterize the composition and morphology of MgBO2(OH) and Mg2B2O5.In addition，effects of reaction conditions,including reactant concentration,reaction temperature,hydrothermal time,and surfactants on morphology of precursor were investigated.</FONT>