This work focused on the preparation and characterization of a promising biochar as a novel solid adsorbent towards CO2. The biochar was prepared by catalytic pyrolysis of waste roasted peanut shell in molten salt; it was characterized by means of SEM-EDS, BET, FTIR, and TGA, followed by determining the adsorption characteristics, such as adsorption capacity, isosteric heat of adsorption, uptake rate, and selectivity via adsorption temperature and gas pressure. The results indicated that the as-prepared biochar had a rich microporous structure with a peak pore size in the range of 0.69-1.3nm, and exhibited a good performance of CO2 adsorption with a capacity of 3.8mmol/g at 273K and 100kPa. Moreover, the adsorption selectivity of CO2 over N-2, O-2, CO, and CH4 was found to be above 12, 11, 8, and 7, respectively. In addition, an interesting phenomenon of an initial increase and then a decrease in the selectivity of CO2/N-2 adsorption with increasing gas pressure was experimentally revealed.