Abstract For the multipurpose usage of water electrolysis gas, the measurements of heat and hydromechanic properties are first prepared, but for the practical usage of such gas, it is most appropriate to adopt the method of gaining thermal energy via combustion. When water electrolysis gas burns, it can have a very high flame temperature and a fast combustion speed because it is produced by premixing hydrogen and oxygen at a stoichiometric mixing ratio state. To make the best use of the high flame temperature and fast combustion speed of water electrolysis gas for processing steel and for manufacturing combustion chambers, confidential data regarding its basic physical properties and flame characteristics must first be gathered. In this study, the results of the calculation of the density, specific gravity, specific heat at constant pressure, heating value, enthalpy, viscosity, and thermal conductivity of water electrolysis gas were examined, along with its combustion property, via numerical simulation. And the maximum flame temperature(2800 °C) of water electrolysis gas is approximately, which is much higher than the maximum flame temperature of the typical city and propane gases when they are burnt in air (1800–2000 °C). And the combustion speed of water electrolysis gas, which is a premixed gas of hydrogen and oxygen, is about 10 m/s when it is burned as it is emitted.