Cover Story：We performed directional differentiation of human embryonic stem cells into cardiomyocytes. In order to explore the mechanisms of cell metabolic phenotype conversion during cardiac lineage differentiation, we conducted real-time quantitative detection of glycolytic and mitochondrial oxidative phosphorylation capabilities of embryonic stem cells, cardiac progenitor cells, and cardiomyocytes during differentiation. GSK3 inhibitor CHIR99021 and Wnt signaling pathway inhibitor IWP2 were used to differentiate human embryonic stem cells into cardiac progenitor cells and cardiomyocytes. Immunocytochemistry was used to detect the expression of human embryonic stem cell markers. Flow cytometry was used to detect the markers of human cardiomyocytes and cardiac progenitor cells. Extracellular flux analysis was used to test the energy metabolic phenotype of human embryonic stem cells, cardiac progenitor cells, and cardiomyocytes. The stemness of human embryonic stem cells remains stable and all express Nanog, OCT4 and SOX2 cell markers. During the differentiation, more than 99% cells expressed cardiac progenitor cell marker Isl1 on the 7th day, and more than 83% of cells expressed the cardiomyocytes marker cTnT on the 14th day. Human embryonic stem cells have the strongest glycolytic metabolism capacity, while cardiomyocytes have the strongest mitochondrial oxidative phosphorylation capability. Cardiac progenitor cells are in the transition stage of the two ways of metabolism. During the differentiation of human embryonic stem cells into cardiomyocytes, cells gradually loss the glycolytic capacity, while the mitochondrial oxidative phosphorylation capacity gradually increases, followed by the cell metabolic phenotype conversion. This research aims to optimize the method of directional differentiation of human embryonic stem cells into cardiomyocytes, reveal the transformation of differentiation-dependent cell energy metabolism, and provide a basis for theoretical research and clinical treatment of cardiovascular diseases.