The invention relates to the field of biological engineering and chemical engineering, and discloses a pretreatment method of lignocellulose. The method includes the following steps of firstly, conducting primary impurity removing on a lignocellulose raw material to remove part of metals; secondly, conducting primary smashing on the lignocellulose raw material with part of metals removed, so the obtained lignocellulose raw material with granularity of 100-150 mm accounts for 80% or above and the powder with granularity lower than 5 mm accounts for not larger than 12%; thirdly, conducting secondary impurity removing on the lignocellulose raw material subjected to primary impurity removing in the second step to remove metallic and nonmetallic impurities; fourthly, conducting secondary smashing on the lignocellulose raw material with the metallic and nonmetallic impurities removed obtained in the third step, so the obtained lignocellulose raw material with granularity of 10-15 mm accountsfor 90% or above. By means of the method, impurities are more thoroughly removed, the recyclable rate of the raw materials is increased, the stable running of the device is ensured, and the pretreatment operation environment is improved.