It is proposed a new type of the thermodynamic cycle in this article. The cycle is mainly composed by Hydrogen Generator (HG), Hydrogen Turbine (HT), Hydrogen-Oxygen Combustor (HOC) and Steam Turbine (ST). The pure hydrogen is generated in HG at high pressure and is heated up. The hydrogen with high pressure and high temperature develops power by flowing through HT. The hydrogen passed through HT is burned with pure oxygen in HOC, and the generated steam provides power by expansion in ST sequentially. Different from the conventional Combined Cycle (CC), this thermodynamic cycle is series-wound by hydrogen turbine and steam turbine. Based on these features this cycle is called as the Hydrogen-Steam Turbine Composite Cycle (HSTCC) in this article. It is indicated that HSTCC has a higher efficiency. It should be a competitive power generating system using the sophisticated turbine technique for hydrogen energy in future.