The invention discloses an enzyme auxiliary agent used in a cotton linen and linen rayon gray fabric oxygen bleaching process, which is prepared by the following raw materials by weight percent: 47-60% of pentahydrate sodium metasilicate, 5-10% of alkaline pectinase, 27-30% of sodium carbonate, 5-8% of nonionic surfactant and 3-5% of chelated dispersing agent. The invention also discloses a preparation method thereof. The auxiliary agent prepared by the invention has the characteristics of effectively removing cottonseed hulls, hemp husks, impurities, natural pigment and the like, smoothing fabric surface, improving natural whiteness, and having soft and gentle feel, good appearance surface, low cost, small energy consumption, safety and environment protection.