The invention relates to the technical field of chemical industry and particularly relates to a production method for preparation of calcium dihydrogen phosphate and by-production of a special fertilizer for cauliflowers. According to the production method, by analyzing the fertilizer demand situation of the cauliflowers and combining with the shortcomings in a preparation process of a calcium dihydrogen phosphate product, a preparation process of the calcium dihydrogen phosphate product and a preparation process of the special fertilizer for the cauliflowers are combined for production, so that the added value of the product in the preparation process of the calcium dihydrogen phosphate product is improved, the purity of the calcium dihydrogen phosphate product is improved, the waste of phosphorus and calcium element resources is reduced, the emission of waste liquid is reduced, and the serious pollution of the ecological environment is avoided.