Abstract: Under dark culture conditions, chlorophyll disappeared in the mutant cells of Cyanobacterium Synechocystis sp. PCC 6803 resulting from deletion of frxC gene. Absorption spectra and calculation indicated that the phycobiliprotein content increased in the chlorophyll - less algal cells. The contents of phycocyanin and allophycocyanin in the chlorophyll- less algal cells were four and six times respectively as much as those in wild- type cells under the same conditions. When wild-type cells grew heterotrophically in dark, the phycobiliprotein content decreased. The contents of phycocyanin and allophycocanin in the heterotrophic cells were 34.5 % and 25.3 % of those in the autotrophic cells grown in light, respectively. In addition, the phycobiliprotem content in the mutant cells with deletion of apcE gene was lower than that of wild - type cells, showing that the protein Lcm encoded by apcE gene was related to the phycobiliprotein content in algal cells.