Abstract: Taking the solar-gas combined cycle composed of trough solar collector and gas-steam combined cycle as the research objective and using Ebsilon software to model,the solar integrated characteristics of the unit under partial load operation were analyzed when the original GTCC system equipment is unchanged,and the turbine expansion capacity,the turbine and low pressure economizer are expanded. The results show that when the existing eauipment lceeps unchanged and solar collector outlet steam parameters are the same as well,the scale of solar integration is limited by turbine capacity. When the gas turbine is reduced from 100% load to 30% load operation,the maximum solar radiation received by the collector increases from 0 MW to 65 MW,and the corresponding net solar power generation efficiency increases from 29.6% to 31.6%. After the steam turbine in original equipment is rebuilt for expansion,the gas turbine is fully loaded,therefore,the maximum net power generation efficiency of solar energy is reduced from 28.5% to 26.5% when the radiation amount of the collector is increased from 24 MW to 120 MW. But when the gas turbine load is above 75%,the area of the low-pressure economizer is increased by 1.2 times,and when the solar integrated scale is 74 MW,the net solar power generation efficiency is increased by about 2%.