The invention discloses a system and technique for preparing nano calcium carbonate and an amino compound fertilizer from coal chemical industry three wastes. Waste sulfuric acid, phosphogypsum, waste ammonia water, CO2 gas and other three wastes generated in different coal chemical industry processes are subjected to overall arrangement and sectionalized utilization to implement the harmless treatment and resource utilization on different coal chemical industry three waste products, thereby solving the problem of difficulty in treating waste sulfuric acid, reducing the stacking of the phosphogypsum, supporting the sustainable development of phosphorus chemical industry, achieving the goals of CO2 emission reduction and resource utilization for the utilization of the CO2 byproduct, and detecting another resource utilization way for diluted waste ammonia water.