Abstract: Biphenyl phenol (BDBP) monomer was first synthesized using 4,4-biphenyl dimethyl ether(BMBP) and 2,6-dimethyl phenol as monomers, toluene-p-sulfonic acid(PTS) as initiator. A new biphenyl cyanate ester resin (BDBPCy) monomer was further prepared by cyaniding BDBP. The molecular structure was characterized via FT-IR and MS. The thermal properties, mechanical properties, dielectric properties, water absorption and the flame retardant property of the cured resin were studied via DSC and DMA, etc. Results showed that the cured resin exhibited excellent heat stability and retardant property with the incorporation of biphenyl into the resin structure, residual mass of 42% in nitrogen at 800 °C, glass-transition temperature of 258 °C, class V-0 by UL-94 flame retardant test. Meanwhile, the large size biphenyl and the methyl of the ortho-position in the structure further improved dielectric properties.