The invention discloses a method for culturing microalgae by using biogas residues as raw materials. The method is characterized by comprising the following steps of: (1) adjusting the pH value of the biogas residues to 10 by using a sodium hydroxide solution with the concentration of 5mol/L, standing the biogas residues at the temperature of 25 DEG C for 12h, placing the biogas residues into a high-pressure sterilizing pot, heating at the temperature of 115 DEG C for 60min, cooling, and then, making a microalga culture medium by using a liquid which is collected through vacuum filtration; (2) microalga culture: selecting chlorella as a microalga strain; and (3) biogas residue nutrient solution culture: adjusting the pH value of the microalga culture medium obtained in the step (1) to 7 by using a hydrochloric acid solution with the concentration of 5mol/L, sterilizing at high pressure for 20min, inoculating the microalga strain in the sterilized microalga culture medium through aseptic operation, and then, placing the microalga strain into a swing bed with the rotating speed of 180rpm to be subjected to shaking culture at the temperature of 28 DEG C and the illumination intensity of 6000Lux for 7 days.