Ammonia-based CO₂ capture technology has crucial impacts on power plants carbon emission reduction, which has become one of the most concerning issues. However, there are limitations faced by traditional capture technology in the absorption rate, ammonia escape and regeneration energy consumption. The functionalized biochar (with a specific surface area of up to 2835.36 m²/g, micropores volume of 77.4 %) was used to enhance the mass transfer process of new ammonia-based (ammonia-ethanol mixed absorbent) CO₂ capture by the bubbling absorption experiment system, combined with Monte Carlo simulations, which explored the adsorption and release characteristics of CO₂/NH₃ molecules in biochar with different pore sizes. The results show that the CO₂ absorption flux added biochar RH-900 is 59.67 L·min, increased by 16.16 % compared with pure absorbent. And the volume mass transfer coefficient is 1.226 × 10^-4mol/m²·s·Pa, increased by 15.3 % compared with the SiO₂. The addition of RH-900 also promotes the CO₂ load capacity of the carbonated solution up to 0.5255 mol/L, enhancing the CO₂ absorption capacity and CO₂ capture efficiency significantly. The ultra-micropores adsorb CO₂, while the surface of larger pores distributes and achieves the adequate fixation of NH₃. Besides, the mesopores and macropores provide space where the CO₂ is transported and diffused, and the free ammonia concentration is maintained. The study provides an innovative thought for improving the ammonia-based CO₂ capture method and significantly reducing of harmful carbon emissions by biomass energy-carbon capture and storage (BECCS) technology.