The β-carotene ketolase gene (bkt) and β-carotene hydroxylase gene (crtR-B) from Haematococcus pluvialis were codon-optimized and transferred to Synechocystis sp. PCC 6803 genome by natural transformation method. High performance liquid chromatography analysis showed that cells transfected with bkt gene produced canthaxanthin, while echinone decreased; the cells with crtR-B gene produced adonixanthin, while zeaxanthin was reduced. The results showed that the exogenous β-carotene ketolase converted echinone to canthaxanthin and the exogenous β-carotene hydroxylase converted zeaxanthin into adonixanthin. In this paper, the pathway of astaxanthin biosynthesis in Synechocystis sp. PCC 6803 was constructed by metabolic engineering strategy, which laid a foundation for astaxanthin production in Synechocystis sp. PCC 6803 with metabolic engineering.