The invention discloses a method based on mixotroph microalgae oil accumulation, and belongs to the technical field of
biodiesel. The method comprises the steps that a BG-11 basal culture medium adopting glucose as a
carbon source is used for cultivating single
algae, and
algae cells are collected when the single
algae grows to the rear
logarithmic growth period; waste fermented liquid is dilutedto be adopted as the basal culture medium for single algae, and then, MgSO4 7H2O is added into the basal culture medium; the PH value is regulated to 6.8-7.1, and the culture medium is prepared; the prepared culture medium is subjected to high-pressure and high-temperature sterilization, oil-producing single algae is inoculated, the algae
cell concentration is 0.9-1 g / L, then, absolute ethyl
alcohol is added for dissolving a
melatonin mother solution, the final concentration of
melatonin in the culture medium is 10<-1>-10<-4> mol / L, and the algae solution is placed into strong light to be cultured; microalgae cultured to the stable stage is enriched, oil is extracted, and
biodiesel is prepared. The method is simple and easy to implement, the production cost can be greatly lowered, the oilyield is remarkably increased, and therefore the
biodiesel production efficiency of microalgae is greatly improved.