Semi-coke is a good adsorbent because of its high fixed carbon content，good reactivity and developed pores. Its surface contains a large number of oxygen functional groups，which is easily modified，often used as an adsorbent or catalyst.More pores and better adsorption capacity can be produced by the modified char. In order to study the influence of chemical modification on the adsorption property of semi-coke，the semi-coke produced by Shenmu gas heat carrier vertical pyrolysis furnace was used as raw material and modified by different modification methods such as acid and alkali. The effects of acid and alkali on the pore structure，morphology，specific surface area，deashing rate and adsorption property of semi-coke were studied by FTIR，SEM and nitrogen adsorption methods. The results show that the ash content of semi-coke is reduced after treatment，and the deashing rate of acid-base combined treatment is up to 89.5%. After acid modification，the number of surface acid oxygen-containing groups such as carboxylic acid and phenolic increase，and the specific surface area，pore volume，pore size and adsorption capacity of methylene blue and iodine value decrease. After alkali modification，the specific surface area，pore volume，pore size and adsorption capacity of methylene blue and iodine value increase，and the number of micropores on the surface increase. The specific surface area and pore volume of micropores are 0.009 7 m²/g and 35.519 4 cm³/g，respectively. The adsorption capacities of methylene blue and iodine are 1.05 mg/g and 714.11 mg/g，showing good adsorption performance. Under different treatment conditions，the adsorption performance of semi-coke is as follows：alkali treatment semi-coke>primary treatment semi-coke > acid-base combined treatment semi-coke>acid treatment semi-coke.