Abstract: A monocyclo-benzoxazine monomer containing alkynyl (P-a) was synthesized and then a new bicycle benzoxazine monomer with conjugated diacetylene structure (CoP-a) was prepared based on the Glaser coupling reaction of the alkynyl group of P-a. The chemical structure of CoP-a was characterized by Fourier Transform Infrared (FT-IR) spectroscopy and Nuclear Magnetic Resonance (NMR). Then, the polymer (P(CoP-a)) was obtained by the stepwise thermal curing reaction of CoP-a and the final curing temperature was 200℃. The curing reaction kinetics of CoP-a was analyzed by Differential Scanning Calorimetry (DSC), and the char yield and degradation kinetics of the polymer were investigated by Thermogravimetric analysis (TG). Based on the Kissinger method and the Ozawa method, the curing reaction activation energies of CoP-a and the thermal degradation activation energies of P(CoP-a) were calculated, respectively. The results showed that CoP-a was synthesized successfully, and the oxazine ring was not affected during the Glaser coupling reaction. The initial curing reaction temperature and the reaction peak temperature of CoP-a were 125℃ and 222℃, respectively. The char yield of P(CoP-a) was as high as 75.6% at 800℃ under nitrogen atmosphere. The curing reaction activation energies of CoP-a calculated by Kissinger method and Ozawa method were 106.2 kJ/mol and 108.8 kJ/mol, and its thermal degradation activation energies of P(CoP-a) were 343.4 kJ/mol and 338.1 kJ/mol, respectively, which were higher than those of many thermosetting resins. The crosslink density of the polymer was increased because of the additional reaction of coupling alkynyl groups, which further increased the thermal stability of the polymer. In summary, this new resin showed good reactivity and high thermal stability, and could be used in the field of ablative materials.