Extracting weak acid soluble phosphate fertilizer and citric acid soluble phosphate fertilizer. The main function of ammonium citrate in phosphate fertilizer is to extract weak acid soluble phosphate fertilizer and citric acid soluble phosphate fertilizer. Using alkaline ammonium citrate solvent to extract citric acid soluble phosphate fertilizer can extract effective phosphorus from phosphate fertilizer, and achieve a complete and sufficient extraction effect of effective phosphate fertilizer.