The invention discloses a method for preparing bio-oil by catalytic liquefaction of microalgae. The method comprises the following steps: (1) adding haematococcus, a solvent methanol and a montmorillonite catalyst supporting transition metal ions to the a heatable reactor in a certain ratio, wherein the reaction temperature is 180 to 240 DEG C and the reaction time is 1 to 3 h, the ratio of the material to the liquid of the haematococcus to methanol is 0.1-0.5g/mL, and the mass ratio of the haematococcus to the catalyst is 1:0.01-0.1; (2) after the reaction is completed, natural cooling the material to room temperature, performing suction filtration on a reaction solution, and collecting a liquid phase product; and (3) distilling the solvent methanol and the low-boiling substance of the liquid phase products to obtain the bio-oil. The catalyst montmorillonite used in the invention has the advantages of wide source and low price. The bio-oil yield obtained by the present invention is greater than 87%, the selectivity is greater than 94%, and the calorific value is greater than 36 MJ/kg. The method has the advantages of high bio-oil yield, high product selectivity and high product calorific value.