Abstract: Abstract: In order to improve the thermal performance of a fixed linear mirror solar concentrator, its working principle was introduced in this paper. The equation of incidence angle and illuminate area had been obtained by vector analysis. At the same time, the 3D model of a cylindrical cavity glass-metal vacuum tube absorber and a fixed linear mirror solar concentrator were established. The Monte Carlo ray tracing method was applied to investigate the concentrating characteristics of the concentrator. The flux distribution on the receiver was simulated and drawn with TracePro software, as a ray trace analysis at different transverse angles determined optical efficiencies, optical loss, and flux distribution of the absorber. The results showed that the overall ray's acceptance of 74.08%-98%and optical efficiency of 56.97%-73.65% were obtained from the transverse angles of 0° to 40°with the mirror reflectance of 0.92 and the receiver absorbance of 0.9. In addition, the thermal performance of the trapezoidal cavity absorber and the cylindrical cavity absorber were studied experimentally at the different transverse angles and output temperatures. The cylindrical cavity glass-metal vacuum tube absorber had a significant advantage in terms of superior thermal performance as compared to the trapezoidal cavity absorber. The thermal efficiency of the cylindrical cavity glass-metal vacuum tube absorber was higher than the trapezoidal cavity absorber by 2%-3% at the low environment temperature and irradiation under the same condition. The thermal efficiency of the cylindrical cavity glass-metal vacuum tube absorber decreased from 46.93% to 39.98% as the output temperature increased from 76.7℃ to 99.6℃.