The invention relates to a synergistic compound fertilizer. The synergistic compound fertilizer comprises, by weight, 0.1-100 parts of a synergist, 0.3-700 parts of a biological preparation, 1-200 parts of calcium sulfate, 5-500 parts of sodium silicate, and 2-8000 parts of a compound fertilizer, wherein the synergist comprises potassium humate, polyaspartate, chitosan, nonionic polyacrylamide, potassium polyacrylate and poly(potassium silicate); and the biological preparation comprises azotobacteria, phosphate-solubilizing bacteria, potassium releasing bacteria, photosynthetic bacteria, actinomyces, microzyme and Bacillus spp, and the quantity of beneficial live bacteria is greater than 2billions / g. The synergistic compound fertilizer adopting the biological preparation comprising azotobacteria, phosphate-solubilizing bacteria, potassium releasing bacteria, photosynthetic bacteria, actinomyces, microzyme and Bacillus spp and the synergist comprising potassium humate, polyaspartate, chitosan, nonionic polyacrylamide, potassium polyacrylate and poly(potassium silicate) has the advantages of effective improvement of the fertilizer utilization rate, increase of the water retention rate, promotion of the growth of crops, improvement of the continuous cropping and disease resistance of a chemical fertilizer, environmental protection and no pollution.