Abstract: To address the challenge of predicting the fire resistance of biomass composite boards, a thermal response numerical model based on combustion tests and pyrolysis kinetics was established. Based on the determination of the material’s pyrolysis kinetics, the high-temperature thermal conductivity was characterized through combustion tests, thereby enhancing the model’s predictive capability. The fire resistance of two types of biomass materials and their composite structures was predicted. The results show that at room temperature, the thermal conductivity of biomass material B is lower than that of material A, whereas at high temperatures, material B exhibits higher thermal conductivity than material A. The ABA composite structure demonstrates better thermal insulation performance than the BAB structure. Predictions of the thermal insulation performance for different biomass panel structures show that the error in backside temperature rise is generally within 20%, and the thickness error is within 8%, validating the reliability of the model. This model can provide a theoretical basis for predicting the fire resistance of biomass composite boards and guide the design of new biomass composite boards.