Abstarct: Abstract In this research, the effect of zinc oxide nanoparticles on the tensile and buckling behavior of glass/epoxy composite under the effect of sunlight has been investigated experimentally. To make glass/epoxy composites, LR620 epoxy resin, H620 hardener, 280g unidirectional glass fibers and zinc oxide nanoparticles from US Nano company were used in the amount of 1% by weight. Composite plates were made by manual porcelain laxyer method and beam-shaped samples were extracted from it with the help of laser cutting. Composite beams have a rectangular cross-section and are subjected to axial pressure load (buckling), tensile force and sunlight simulator. The sunlight simulator has a 3000W Xenon lamp from Germany and radiates heat and sunlight to the part according to sunlight standards. The results show an increase in the critical buckling load and tensile strength and prevent the destructive effect of sunlight on glass/epoxy composites by adding 1% by weight of zinc oxide nanoparticles to the baxse material. baxsed on the results of experimental tests, sunlight has a less destructive effect on tensile strength and critical buckling load of glass/epoxy composite samples containing 1% zinc oxide nanoparticles. Also, in order to investigate the distribution of zinc oxide nanoparticles in the background and its effect on the strength and adhesion between the background material and the fibers in the glass/epoxy composites, the cross-sectional surface of the samples was imaged by a scanning electron microscope. Also, the experimental results were compared with the simulation results obtained from Abaqus finite element software, which shows that the numerical and experimental results are in good agreement with each other.