The invention provides a pretreatment method of lignocellulose and the prepared lignocellulose. The pretreatment method comprises the following steps: smashing a lignocellulose material, and carrying out compression forming; placing the obtained lignocellulose material into a closed reactor, under the constant temperature condition, introducing carbon dioxide into the reactor, maintaining the pressure for 1-5 h under the constant pressure, and then reducing the pressure to the normal pressure, thus obtaining the pretreated lignocellulose, wherein the time needed for reducing the pressure to the normal pressure after the pressure maintaining operation is 8-15 min. According to the pretreatment method and the prepared lignocellulose, by utilizing the superstrong solution-pervasion capacity of carbon dioxide under the super-critical state, carbon dioxide permeates into a net-shaped crystalline structure of cellulose small particles formed through smashing and compression forming under the fixed temperature and pressure conditions, then decompression is carried out to enable carbon dioxide to escape, thus the strong interaction among covalent bonds, hydrogen bonds and the like formed among cellulose, hemicellulose and lignin is damaged, and finally, the effective separation of cellulose, hemicellulose and lignin is realized.