The main constitution and the performance characteristic of Solar Thermal Power System (STPS) were introduced, and the thermal losses law of the recycled working substance of the conventional thermal power generation unit was analyzed in this paper. The key technical choke points currently existing in high-temperature solar thermal power system were demonstrated in the aspect of technical feasibility and economical efficiency. And then, the combined operation scheme of solar thermal power and conventional thermal power was introduced in this paper. In this hybrid system, the normal and low temperature water vapor can be obtained by solar power and utilized efficiently, in additional, those technical choke points existing in high-temperature solar thermal power can be avoided. With higher comprehensive efficiency and obvious technical and economic performance, the combined operation of solar thermal power and conventional thermal power can be the most important alternative scheme in the reformation progress of the energy conservation and environment protection in conventional thermal power plants, and the most significant way to utilize solar power efficiently.