This paper presents a study of the Hydrogen/Argon lifted flames in a hot vitiated co-flow. The effects of the dilution of argon in central fuel, the volume fraction of argon in the central fuel, co-flow temperature and the velocity of the central jet on the lift-off height were studied, and the numerical simulation with PDF model were analyzed as well. This study could provide theoretical supports for the research of the hydrogen fueled argon cycle engine which is a potential way to increase the indicated thermal efficiency of internal combustion engine and realize the zero emission. In this study, the volume fraction of argon in central fuel is 20%, 25% and 30%; the co-flow temperature ranges from 1009 K to 1197 K at an ambient pressure of 1 atm; the velocity of the central jet ranges from 76 m/s to 129 m/s. The experimental results show that adding Ar in central fuel has a substantial influence on the jet flame characteristics, which could reduce the lift-off height. Because it can decrease the specific heat capacity of the mixture of the central jet, the temperature of the combustion zone increases as a result, which means that the adding of Ar could enhance the combustion reaction. When volume fraction of argon in central fuel increases, the lift-off height rises, which means that the central fuel with the small volume fraction of hydrogen needs additional time to form combustible mixture. The lift-off height decreases with co-flow temperature increased, which means that the high co-flow temperature is favorable to the mixture of jet and co-flow and the auto-ignition of the combustible mixture. When the velocity of the central jet increases, the lift-off height rises slightly at high temperature of the co-flow, which means that the stability of the flame here is determined by flame propagation velocity. The numerical simulation is used to obtain the temperature distribution and concentrations of the major species, OH. The radial profiles and axial distribution of important species reveal the effect of adding Ar in the central fuel on the acceleration of combustion reactions.