The invention provides a chitin modified ES composite fiber. The chitin modified ES composite fiber is a skin-core type fiber and is prepared by at high pressure extruding, spraying and compounding the two components of multifunctional skin masterbatch and core masterbatch at a weight ratio of 50-65:20-25 with a spinning nozzle. The chitin modified ES composite fiber achieves a breaking strength of 4.5-5.2 N/tex, a percentage of elongation of 3.2-3.4%, a modulus of 150-164 N/tex and a melting point under stress of 166-168 DEG C; the core masterbatch is high-melting-index PP (polypropylene) with an MFR (melt flow rate) of 750-1350 g/10 min and a melting point of 150-165 DEG C. The chitin modified ES composite fiber is based on the antibacterial properties of chitin to achieve the antibacterial objective and acquire high antibacterial and mildew-proof properties, and based on the feature of high compatibility of the chitin with human body, can achieve antiallergic and skincare effects.