Peat was sampled, crushed, ground, impregnated with H3PO4, briquetted and re-crushed, then a series of activated carbon samples were prepared by activation in tube furnace at different temperature and time. Thermogravimetric analysis of H3PO4 impregnated peat samples were performed in a nitrogen environment. The adsorption capacity indexes including iodine value, methylene blue value and caramel decolorization rate were determined, and pore structure, carbonaceous structure, surface chemistry and micro morphology of activated carbon samples were characterized by gas adsorption instrument, Raman spectroscopy, infrared spectrum and scanning electron microscope, respectively. The results show that peat is cross-linked during phosphoric acid activation, and the maximum mass-loss temperature of carbonization/activation drops from around 300℃ to ca. 200℃. With the increase of H3PO4 impregnation ratio and activation temperature, content of irregular graphitic layers in activated carbon increases, and hydroxyls groups on surface of activated carbon decreases. The increase of H3PO4 impregnation ratio results in gradual increase of pore development, absorption performance and volume of 2—5 nm pores. And the increase of activation temperature results in shrink firstly (at 400—550℃) and then destroy ( at 600℃) of pore structure , decrease of absorption performance and volume of 2—5 nm pores. With the increase of activation time, the content of hydroxyl groups on surface of activated carbon firstly reduces greatly (during 120—150 min) and then undergoes irregular changes, meanwhile, the pores firstly expand (during 120—180 min) and then shrink (>180 min), and the absorption performance reduce rapidly after 180 min, at the same time the carbon structure and the volume of 2—5 nm pore section don t show significant change. An activated carbon with a specific surface area of 678.52m2·g-1, volume of 2—5 nm pores of 0.1475 cm3·g-1, accounting for 31.04% of the total pore volume and 70.24% of the mesopore volume, can be derived under the conditions of H3PO4 impregnation ratio 1.5, activation temperature 500℃, and activation time 180 min.