Abstract: Benzoxazine monomers with methyl group (Bm) and benzyl group (Ba) in bisphenol A backbone were synthesized. The effects of curing temperature and curing time on the surface free energy of the polybenzoxazines film were investigated. The film formation property and thermal stability of polybenzoxazines were also studied. The lowest surface free energies of the polybenzoxazines films (16.0 and 16.6 mJ/m2) are obtained by curing Bm and Ba at 210 ℃ for 1 h, which are even lower than that of Teflon (22.0 mJ/m2). The rootmeansquare roughness of PBm and PBa polybenzoxazine films were 0.4 nm and 0.2 nm, respectively. Temperatures at 5% weight loss for the PBm and PBa are 279 ℃ and 335 ℃, respectively. The thermal stability of PBa polybenzoxazine is better than that of PBm.