Utilizing multi energy sources synthetically is one of the trends of energy utilization. China has splendid solar energy resource, however, the majority of the electricity production still comes from coal-fired power plants. It is of great necessity to investigate the solar-coal complementary electric generation technology. A 300MW unit thermal-circulation boiler has been studied; calculations about the wall circulation characteristics have been made under 40 conditions. The influence of solar-energy utilization on wall circulation has been analyzed. Calculation and analysis indicated the following: the utilization of solar energy has prominent influences on the steaming point and the under-heating condition of the drum water; the solar energy could be used at high load or low load with the high pressure heaters bypassed conditions, but should not used at 60%-70% load.