The invention discloses an oilseed rape blanket-shaped nursery special matrix and its preparation method. The matrix comprises mushroom residue treated by fermentation and decomposition, acid-sludge,manioc waste mixed fermenting material and coco coir, carbon bran, plant ash and turf, vermiculite, and perlite. The matrix is prepared from, by volume, 20-30 parts of fermenting material, 10-20 partsof coco coir, 5-10 parts of turf, 5-10 parts of vermiculite, 5-10 parts of perlite, and 3-5 parts of carbon bran or plant ash. Besides, the matrix is further added with 0.3-0.5% by total weight of composite fertilizer and 0.1-0.3% of synergist. The preparation method of the matrix includes raw material selection and processing, material fermentation, matching and mixing, fertilizer blending, testing and adjustment of physicochemical indexes, quantitative packing, and other steps. The matrix is high in nutrition content, stable in structure, good in blanket forming effect and has a certain fiber; the matrix is very suitable for cultivate oilseed rape blanket-shaped nursery; compared with seedbed soil nursery, the seed nursery rate is improved by about 10%; after sprouting, the surviving rate is improved by about 15%; the tidiness of the height of seedling is improved by 15-20%' the difference of the average tidiness of 10 disks of seedlings is reduced by 15-20%.