The invention relates to a slow-release type nitrogen-phosphorus-potassium composite fertilizer and a production method thereof, belonging to a composite fertilizer with slow-release type nutrient. The composite fertilizer is characterized by comprising the following components by weight portions: 5 to 50 of slow-release composition of phosphogypsum and fly ash, 10 to 40 of urea, 10 to 45 of hydrochloric acidified phosphate rock powder, 10 to 35 of mixed potassic fertilizer, 0.5 to 2.0 of slow-release agent and 1 to 5 of trace element compound. The raw materials are mixed evenly, the conventional auxiliary materials are added for granulation, and then lamination is carried out so as to obtain the composite fertilizer. The invention provides an ideal slow-release type nitrogen-phosphorus-potassium composite fertilizer which has comprehensive nutrients, scientific and reasonable matching and slow rate of fertilizer decomposition and nutrient release, is in conformity with the absorption rate of plants for nutrients, can improve the yield and quality of agriculture product, improve utilization rate of fertilizer, reduce rate of fertilizer application and agricultural production cost, and is beneficial to protection of soil and natural environment and a production method thereof.