Abstract: Effects of SiO₂^- content on microstructure and properties of high pure beryllium oxide high thermal conductive ceramic prepared by solid state react method were investigated.The results revealed that with the increase of SiO₂ content,flexural strength,density,thermal conductivity and electric properties increases first and then slightly decreases.The sample with 0.8% SiO₂(mass faction)have excellent properties and denser microstructure,with the flexural strength of 248 MPa,density of 2.957 g/cm³,the thermal conductivity of 303 W/(m·K).