An apparatus for heating a working fluid of a gas turbine-solar power generation system, comprising, sequentially connected, a cold air flow channel, a heat collecting cavity, and a hot air passage. The hot air passage is formed by connecting an inner housing on the front side to a supplemental heating section on the rear side. Also comprised is a burner for heating a primary heating air within the supplemental heating section when having insufficient solar power, and the burner is arranged at the supplemental heating section.