Abstract: To explore the mechanism of phosphorus limitation adaptation in cyanobacteria, a possible phosphorus regulatory gene, phoR (A2100), was identified in Synechococcus sp. PCC 7002. The results of bioinformatics analysis showed that the length of phoR was 1296 bp, encoding 431 amino acids. PhoR comprises a PAS domain, a HisKA domain and a HATPase_c domain, with a theoretical isoelectric point of 5.20 and a predicted molecular weight of 49.58 kD. In addition, the sequence of PhoR is relatively conserved in different cyanobacteria species. Subsequently, the PhoR recombinant protein was expressed in E. coli, and a murine polyclonal antibody was prepared to detect the expression in Synechococcus sp. PCC 7002 under the phosphorus deprivation induction. The results indicated that the expression of PhoR was significantly induced in response to P deficiency. Then, we generated the Mut-phoR mutant strain through deletion mutagenesis and analyzed its physiological phenotype. It was found that Mut-phoR exhibited notable growth defects and impaired photosynthesis under phosphate limitation. This study provides a scientific basis for further understanding on the molecular mechanism of phosphate deficiency adaptation in cyanobacteria.