The invention relates to the field of surface modifying of synthetic fiber, and discloses a method for quickly depositing dopamine or derivative thereof onto surface of synthetic fiber in a non-water medium environment. The method comprises the following steps of (1) performing hydrophilic treatment on a synthetic fiber fabric; (2) soaking and pretreating the synthetic fiber fabric by an alkaline solution; (3) adding the dopamine or derivative thereof into a non-water medium, stirring, and uniformly dispersing the dopamine or derivative thereof into the medium; (4) soaking the synthetic fiber fabric into the non-water medium, stirring, fetching out the fabric, flushing, and drying. The method has the advantages that the surface of the synthetic fiber is treated by a plasma technique, the obtained hydrophilic surface can adsorb the alkaline liquid, and the water-soluble dopamine or derivative thereof is used for modifying the surface of the synthetic fiber in the non-water medium environment; the dopamine or derivative thereof can be uniformly deposited onto the synthetic fiber by adopting the method, the time is short, the utilization rate of the dopamine or derivative thereof is high, and the universality is strong.