Abstract: The purpose was to identify the main component pigment in Shanlan and study its antioxidant activity.The pigment was separated from Shanlan by using D101 macroporous resin column chromatography and preparative high performance liquid chromatography.The structure of the pigment was identified by using UV, IR, 1H-NMR and MS, and its antioxidant activities were detected and evaluated by DPPH and reducing power of Fe3+.The result showed that the main component about the pigment in Shanlan was 2-amino-7, 8-dimethoxy-3H-phenoxazine-3-one, and the pigment has a certain degree of antioxidant activity in DPPH· test and reduction test.This test identified the main component about pigment, and it had a strong antioxidant activity, this method could be used as the basis for the further research of Shanlan.