The invention discloses a method for preparing an oyster mushroom cultivation material by utilizing a marigold straw. The method comprises the following steps of drying the marigold straw, then grinding and removing marigold leaves, and crushing the ground marigold straw till a granule length is 1-20mm; uniformly mixing the following materials in parts by weight: 30-60 parts of crushed marigold straws, 20-50 parts of corncob granules of 30-40 meshes, 10-20 parts of corn flour, 1-5 parts of glucose and 1-5 parts of gypsum to obtain a mixture A; uniformly mixing the mixture A and water to obtain a mixture B; concentrating the mixture B into a pile, covering the pile by using a conventional agricultural film, sealing for 2 hours, and then sterilizing for 180-190 minutes to obtain the oyster mushroom cultivation material, wherein the sterilizing temperature is 121-125 DEG C. The method disclosed by the invention is simple, can be used for ecologically and efficiently utilizing the marigold straw by providing a new marigold straw utilization method and lays a foundation for using oyster mushroom bran for preparing a nematicidal organic fertilizer.