Abstract: Phaeocystis has attracted much attention because of its high frequency of causing a large area of harmful algal blooms by colonies form.Therefore, the colony formation of Phaeocystis plays an important role in the ecological competition and the occurrence and development of Phaeocystis bloom.More and more studies have shown that diatoms are closely related to the colony formation of Phaeocystis.Here, the progress on the studies of the correlation between diatom and colony formation of Phaeocystis was reviewed.The detailed information includes the discovery of the adhesion phenomenon between diatoms and the colony of Phaeocystis; the phenomenon of diatoms involved in the algae life history of Phaeocystis; the role of diatoms in promoting colony formation of Phaeocystis; species selectivity associated with Phaeocystis when it attach to diatoms species; and the relationship of coexistence of diatom and Phaeocystis.All the progress would provide us an understanding of the ecological role and significance of diatoms involving in the occurrence and development of Phaeocystis.