Abstract: The physicochemicaland adsorption characteristics of themicrowave hydrocharswere discussed by using pure water,phosphoric acid,citric acid,acetic acid and sulfuric acid solutions as the hydrothermal reaction media.The results showed that the addition ofacid media reduced the yield of hydrochar. The addition of phosphoric acid solution medium resulted in the highest yield of hydrochar,which was 44.25%-47.24%. Compared to that preparedin pure water medium,the C,ash and fixed carbon of hydrochar prepared in acid media were higher,while the H/C and O/C were lower. The application of acid mediaenhanced the C==O,C==C and aromatic C—H bonds in the hydrochar. The hydrochars prepared in the phosphoric acid medium had the most abundant pore structures and carbon microspheres,followed by those prepared in the citric acid medium. The phosphoric acid medium resulted in the largest specific surface area of 10.669-15.506 m2/g and the largest total pore volume of 0.070-0.116 cm3/g of the hydrochar.The hydrochars prepared in acid media had a significant increase in the adsorption amount of ammonia nitrogen,and those prepared in phosphoric acid medium had the highest adsorption amount of ammonia nitrogen of 5.26 mg/g. The contents of ash,fixed carbon,C,N and O of hydrochars had a positive impact on the adsorption of ammonia nitrogen,meanwhile,the adsorption of ammonia nitrogen were also positively correlated with the specific surface area,total pore volumeand aperture size of the hydrochar.