A bio-enzyme for catalyzing synthesis of phosphatidylserine, a preparation method therefor and application thereof. The bio-enzyme is an amino acid sequence represented by SEQ ID NO : 2. The preparation of the bio-enzyme comprises : first constructing a genetic engineering strain of a bio-enzyme; by using bio-enzyme gene fragments synthesized by whole gene synthesis, linearizing recombinant plasmids with restriction enzyme Sal I, for expressing the bio-enzyme; and performing further fermentation to obtain the bio-enzyme for catalyzing synthesis of phosphatidylserine. By utilizing high specificity of phosphatidylserine in synthesis of enzyme to catalyze the preparation of phosphatidylserine from lecithin and serine, the conversion rate reaches 80%, and thus the problem of being unable to obtain high-purity phosphatidylserine by using the existing extraction method and chemical synthesis method is effectively resolved. Moreover, the present invention is stable and reliable in process, high in efficiency and suitable for industrial production, and has great application potential in the fields of medicines and food healthcare products.