The invention discloses a method for culturing microalgae by adding an anaerobic digestion liquid of kitchen waste into natural seawater, aims to find out the best proportion, and belongs to the technical field of the microalgae. According to the invention, the digestion liquid is added to natural seawater according to the ratio of (1:10)-(1:50) to be taken as an experimental group culture medium, BG11, natural seawater and the digestion liquid are taken as a control group, the experimental group culture medium is cultured under the condition of continuous light until the microalgae stops to grow, and centrifugal separation is carried out to obtain the microalgae. The result shows that the growth rate of the microalgae added with the digestion liquid and cultured in natural seawater is obviously higher than that of the microalgae cultured in the BG 11 and pure seawater, furthermore, natural seawater added with the digestion liquid is taken as the culture medium to improve the lipid yield of the microalgae and lower the cultivation cost of the microalgae, so that the method for culturing the microalgae by adding the anaerobic digestion liquid of the kitchen waste to natural seawater is worthy of being popularized and applied.