Aiming at the interaction of phosphorus and trace element iron on the growth of algae, the interaction characteristics of phosphorus and iron in the growth and toxicity of algal cells were studied under different phosphorus sources. Microcystis aeruginosa was selected as algae species, and nitrate nitrogen was used as nitrogen source. Dipotassium hydrogen phosphate(K₂HPO₄), small molecular organic phosphorus sodium glycerophosphate(NaGly)and macromolecular organophosphorus lecithin(LEC)were used as phosphorus sources respectively. The growth and toxicity of algae under different iron(Fe³⁺)concentrations were simultaneously investigated. The results showed that K₂HPO₄ and NaGly were the phosphorus sources preferentially used by algae cells. Under these two phosphorus sources, the growth and toxicity of algae cells were promoted, and the average particle size of algae cells remained stable with the incubation time. LEC was not conducive to the growth and toxicity of algae cells, and the average size of algae cells fluctuated greatly. During logarithmic growth period, chlorophyll a was positively correlated with intracellular algae toxin(MC-LR), but there was no correlation between total intracellular phosphorus and total alkaline phosphatase activity(APA)in algae solution. The effect of trace element iron on the growth of algae cells was different under different phosphorus sources and the synergistic effect of NaGly and iron was more conducive to the growth and toxicity of algae cells.