The modular modeling method was adopted to establish the prediction model of gas turbine under offdesign conditions. The operating parameters, component operating characteristics and energy consumption of gas turbine at different loads were calculated and analyzed when hydrogen blending ratio is 0 to 100%. The results show that the air mass flow rate and the surge margin of compressor decrease with the increase of hydrogen blending ratio. However, due to the increase of the pressure ratio, the effective specific enthalpy drop of the turbine increases and the power of the unit increases. Moreover, the power generation efficiency of the gas turbine is improved under the condition of high hydrogen blending ratio. Compared with the condition of pure natural gas, the power generation efficiency of the gas turbine at full load can be increased by 0.03%, 0.06%, 0.14% and 0.86% respectively at hydrogen blending ratios of 10%, 20%, 40% and 100%.