The concentrating characteristics with the glass thickness of reflector of the solar parabolic trough system are studied by theoretical analysis, simulation, and experiments. The results show that the thicker glass of the reflector and the farther distance of the incident light from the optical axis, the bigger both ΔX and ΔY are. The theoretical analysis has been done for the solar parabolic trough system whose focal length is 1200 mm, and the refractive index of glass of reflector is 1.6. For 1-mm thickness glass of reflector, when the distance from the optical axis of the incident light is 200 mm and 2000 mm respectively, ΔX is 0.03 mm and 1.69 mm respectively, ΔY is 0.19 mm and 0.31 mm respectively. For 5-mm thickness glass of reflector, when the distance from the optical axis of the incident light still is 2000 mm, ΔX is 8.41 mm, and ΔY is 1.55 mm. The theoretical analysis is consistent with TracePro simulation and experiments. The research can provide references to further design of solar parabolic trough system.