A new cavity receiver was proposed to improve the efficiency of dish Stirling solar thermal power generation system. The performances of new cavity receiver and its influence were investigated in a 25kW dish Stirling solar system. The results show that the convective and radiative heat losses of the modified cavity receiver are 56.3% and 38.6% of that of the cylindrical receiver and the efficiency of new dish stirling solar power generation system reaches 35.5%, 5.9% higher than that of the dish stirling solar power generation system with the cylindrical heat receiver.