[Objective] Mutants of Aurantiochytrium sp. PKU#SW7 were screened for high docosahexanoic acid (DHA) yield. [Methods] UV mutagenesis and chemical stress screening were used to mutate Aurantiochytrium sp. PKU#SW7, with biomass production, lipid content and DHA yield as screening criteria to obtain mutant strains. [Results] Mutant PKU#PM003 presented stable high DHA yield in 4 generations. In lab fermentation the biomass of this strain reached 6.62 g/L, improved by 11.26% compared to that of the original wild strain; the lipid content of the mutant reached 4.01 g/L, improved by 26.1% compared to the original. The DHA content in total fatty acids also increased from 29.97% to 33.43% and the DHA yield of PKU#PM003 increased by 41.1%. [Conclusion] The mutant stain PKU# PM003 could be used as a potential strain for industrial fermentation.