The invention discloses a lignin-epoxy resin composite material and a preparation method thereof, relates to a lignin-polymer composite material and a preparation method thereof, and aims to solve the conventional problem of low effective utilization rate of lignin. The lignin-epoxy resin composite material uses the lignin as a substrate; epoxy resin, a curing agent, a toughening agent, and the like are evenly blended with the lignin; and through the processes of pre-pressing, hot-pressing and curing molding, the lignin-based composite material is obtained. The lignin-epoxy resin composite material disclosed by the invention has the advantages of little water absorption, good mechanical performance, degradability, and the like, is suitable for manufacturing floor boards, wall protection boards, construction formworks, door-window profiles, fences, guardrails, louvers, roof boards, and the like in the construction industry, can be used for manufacturing inner decorative boards of automobile doors, seat backing boards, automobile roof lining, and the like in the automobile industry, and can also be used in the fields of the packaging and transportation industry, the furniture industry, office articles, sports facilities, and the like.