Solar reflecting and heat collecting systems are generally operated outdoors year-round,and the optical performance of the reflector is reduced by dust accumulation on the surface.In this study,the dust accumulation on a linear Fresnel reflector was investigated.The relative reflectivity of the mirror before and after dust accumulation and the physical and chemical charactersfics of the dust were measured using an ultraviolet spectrophotometer,scanning electron microscope,and X-ray diffractometer.The results showed that the dust density on the mirror increased,and the relative reflectivity decreased with an increase in the dust accumulation time.During 48 days of dust accumulation,the average relative reflectivity decreased 9.4％ for a 1 g/m2 increase in the dust density.Additionally,the dust density on the mirror increased while the relative reflectivity decreased with a decrease in the mirror tilt angle.The rate of decrease of the relative reflectivity was higher for the aluminum mirror than that of the silver mirror after dust accumulation.The main component of the dust particles in the test area was SiO2,and the particle size range of the dust was 0.9 μm to 87 μm.According to the physical and chemical properties of the dust and the shielding effect of the dust on the mirror,a model to predict the influence of natural dust accumulation on the relative reflectivity of the linear Fresnel reflector was proposed.The predicted results deviated about 1％ from the test results.