A towered solar thermal power plant using a recompression supercritical CO

2

Brayton(SCO

2

)cycle with molten salt as the heat transfer fluid was established to improve the performance of solar thermal power plant. The exergy analysis on the subsystems of the heliostat field

the cavity receiver and the recompression SCO

2

power cycle was performed. The effects of direct normal irradiation(DNI)and the type of SCO

2

power cycle with different bottoming cycles on the system performance were tested

and the performances of solar

power plants using different power cycles of SCO

2

and steam power cycles were compared. The results show that: although the heat receiver has a least energy loss

it has the largest exergy loss rate; as DNI increases

the thermal and exergy efficiencies of the receiver and the whole plant increase; and adding a bottoming cycle such as ORC or TCO

2

cycle to recover the waste heat of SCO

2

power cycle can increase the overall efficiency. Especially

the SCO

2

-TCO

2

cycle can achieve higher thermal efficiency

and various SCO

2

cycles can achieve higher thermal and exergy efficiencies compared with steam power cycles under the same conditions. The towered solar thermal power plant using a SCO

2

-TCO

2

cycle has higher cycle efficiency compared with other configurations.