Abstract: Iron phosphate dihydrate was synthesized by precipitation method with ferric chloride hexahydrate and phosphoric acid as raw materials.Surfactant CTAB，was used to prevent particle growth and reunion.By experimental analysis on the impact of various factors on particle size of iron phosphate dihydrate，the better synthesis conditions were obtained as follows：material mix ratio was 1.50∶1（amount-of-substance ratio of P to Fe），reaction temperature was 85 ℃，and dosage of the surfactant CTAB was 1.5% of the quantity of ferric.Under those conditions，well-distributed monoclinic iron phosphate dihydrate powder with 1.5 μm of average grain size and good dispersibility was obtained.

Key words: iron phosphate dihydrate, ferric chloride hexahydrate, phosphoric acid, precipitation method