The invention provides a slow release compound fertilizer applicable to plantation of cotton. The slow release compound fertilizer is a mixture of a plurality of fertilizers and components with no special fertilizer efficiency and is characterized by being prepared from the following raw materials by mass: 25 to 35 parts of urea, 10 to 35 parts of potassium chloride, 10 to 30 parts of ammonium chloride, 10 to 25 parts of ammonium sulfate, 10 to 30 parts of a mixed phosphate fertilizer, 7 to 10 parts of a granulating agent and a proper amount of water. A preparation method for the slow release compound fertilizer comprises the following steps: (1) preparation of a compound of a potash fertilizer and a nitrogen fertilizer; (2) preparation of the mixed phosphate fertilizer; (3) preparation of mixed particles of the components of the compound fertilizer; (4) coating with stearic acid; (5) powder spreading of a modified zeolite powder material; and (6) screening, metering, quality inspection and packaging of qualified fertilizer. The slow release compound fertilizer applicable to plantation of cotton provided by the invention has overall nutrients and excellent slow releasing performance, can fully satisfy demands for nutrients by cotton, enables fertilizer effectiveness to be maximumly performed, improves both output and quality of cotton, saves resources, protects the environment and has low manufacturing cost and a low sale price.