Spent tire is a kind of solid waste with large production, accumulation and great pollution. Spent tire charis the primary product of tire harmless disposal. Its commercial value is enhanced by modification. In thisstudy, K-N co-doped activated carbon was prepared by using spent tire char as raw material, KOH andmelamine as activator and dopant to enhance CO2 capture. In comparison with traditional process, thereasons for the decrease in specific surface area and pore volume caused by K doped have been identified,and a potential doped mechanism has been proposed. It was determined that pyridine nitrogen in theamino functional group played a key role in CO2 adsorption. Meanwhile, the synergistic intensificationof CO2 adsorption by potassium phenolic and pyridine nitrogen was verified by simplified model simulation. The precise K-N doping significantly intensify the CO2 adsorption capacity of spent tire char from0.45 to 2.60 mmol/g (1 bar, 0℃), an increase of 4.78 times. Thermodynamic studies have demonstratedthat the Langmuir model accurately describes the adsorption process, and the adsorption reaction takesplace spontaneously at temperatures below 80.52 C. This work presents an efficient process for upgradingspent tire char, and a novel method of co-treating waste and CO2.