The invention relates to a rubber composite material filled by cardanol modified lignin and a preparation method thereof. The rubber composite material is characterized by being made of 100 parts by weight of rubber and 10-200 parts by weight of cardanol modified lignin. The rubber is natural rubber, polyisoprene rubber, styrene butadiene rubber, butadiene rubber, 1, 2 polybutadiene, an ethylene propylene diene monomer, butyl rubber, nitrile rubber or neoprene, or a combinationof two or more of natural rubber, polyisoprene rubber, styrene butadiene rubber, butadiene rubber, 1, 2 polybutadiene, an ethylene propylene diene monomer, butyl rubber, nitrile rubber and neoprene. The cardanol modified lignin contains hydroxymethyl and unsaturated alkyl long chain functional groups. The cardanol modified lignin is obtained by employing ormaldehyde and cardanol as modifiers to modify a black liquor or pure lignin. According to the invention, environment friendly and renewable lignin and cardanol are taken as the main raw materials, which can improve the mechanical properties of the rubber products and lower the rubber product cost. Thus, the rubber composite material filled by cardanol modified lignin has economic value and social significance.