The invention discloses a bamboo fiber / polylactic acid composite material and a preparation method thereof. The bamboo fiber / polylactic acid composite material specifically comprises the following rawmaterials in parts by weight: 60-80 parts of polylactic acid, 10-30 parts of talcum powder, 3-15 parts of modified bamboo fibers, 2-15 parts of a flexibilizer, 0.1-0.3 part of a coupling agent, 0.1-0.3 part of an antioxidant, 0.2-0.6 part of an auxiliary antioxidant, 0.2-0.5 part of a lubricating agent, 0.2-1 part of a nucleating agent, 0.1-0.3 part of an anti-floating fiber agent and 0.5-3 partsof a hydrolysis resistance agent. According to the composite material disclosed by the invention, the bamboo fibers are modified and thermally treated, the bamboo fibers and talcum powder are treatedby using the coupling agent, and according to a certain mixing sequence and suitable extrusion process parameters, the problems that the bamboo fiber / polylactic acid composite material is rough in surface and has silver filaments and local black spots and the compatibility between the polylactic acid and the bamboo fibers is poor are solved.