As a kind of medium-high temperature solar collector, trough concentrating solar collector can obtain higher heat collecting temperature, which can be used in power generation, refrigeration and air conditioning, heating, seawater desalination and other production and life fields. The absorber of traditional trough solar collector adopts vacuum glass tube structure, that is, the inner tube adopts metal tube, the heating medium passes through the tube, the metal tube is coated with selective absorption coating, and then the glass tube is outside, and vacuum is pumped between the glass tube and the metal tube to inhibit convection and conduction heat loss. Because of the different expansion coefficients of glass and metal sealing, the absorber with this structure has high cost and short service life, which affects the reliability. In this paper, a cavity absorber structure is proposed, which does not use glass vacuum tube structure, but suppresses the radiation and convection losses of the absorber through the principle of radiation cavity heat exchange, and achieves good results. In this paper, four kinds of cavity absorbers which can be used in trough focused solar collectors are analyzed in detail. These four cavity structures are triangular, square, circular and semi-circular. Thermal performance is modeled and analyzed based on FLUENT, and optical performance is modeled and analyzed based on TracePro. Thermal performance analysis includes the effects of different heat absorption surface temperatures (90℃ and 150℃), inclination angle α and different glass cover shapes on heat loss. An experimental device for optical efficiency test and optimal opening width test with Fresnel lens as condenser was set up. It is found that the triangular cavity has the best optical efficiency, and the heat loss test of each cavity shows that the triangular cavity has the best thermal performance.