Abstract: Coal gangue as industrial solid waste, replacing all aggregates to produce concrete, is an effective way to reuse coal gangue. In this paper, all the coarse and fine aggregates of concrete were replaced by crushed coal gangue aggregate, and modified by different amounts of nano-SiO₂ and polypropylene fiber (PPF). Based on the combination of macro mechanics and micro analysis, the effects of the single and combined action of nano-SiO₂ and PPF on the mechanical properties and microstructure of concrete were studied. The results show that the performance of concrete is the best when the mixture of nano-SiO₂ and PPF is 1.5wt% and 0.6 kg·m⁻³, respectively. Compared with the control group, the compressive strength, flexural strength and splitting strength of the concrete at 7 days increase by 21.8%, 43.5% and 44.4%, respectively. Besides, the compressive strength, flexural strength and splitting strength at 28 days increase by 20%, 44.9% and 43.6%, respectively. The microstructure analysis shows that the porosity of coal gangue concrete decreases, the hydration process is accelerated, the fractal dimension of large holes of the concrete increases from 2.9975 to 2.9990, while that of small holes decreases from 2.9852 to 2.9827, the fractal dimension of small holes decreases, and the fractal dimension of large holes increases, so that the stronger the space filling capacity, the fewer internal pores.