Precipitation of calcium phosphate leads to pipeline blockage during irrigation with water-soluble fertilizer. To address this problem, mineralized fulvic acid, which has good biological compatibility and high-water solubility, was modified to improve solubility of calcium phosphate. Mineralized fulvic acid was used with potassium persulfate (K2S2O8), as initiator, and acrylic acid, as the graft monomer, to synthesize a modified mineralized fulvic acid that was investigated as a solubilizing agent for anti-scaling and dispersing properties of calcium phosphate. Optimum process conditions used an initiator dosage of 20% and monomer ratio of 1:1. The carboxyl group content of modified mineralized fulvic acid was significantly increased compared with unmodified mineralized fulvic acid under these reaction conditions. The modified mineralized fulvic acid product easily chelated with calcium ions, which significantly increased dispersibility of calcium phosphate in solution and effectively inhibited its precipitation. The anti-scaling of calcium phosphate reached 97.14%. The results proved that MMFA significantly enhanced the complexation of calcium ions and greatly improved resistance to solubilizing and dispersion of calcium phosphate.