The gold tailing composite sand was used as fine aggregate to replace natural sand, the effect of gold tailing composite sand replacement rate on workability, compressive strength and durability of C30~C50 concrete were studied, and the microstructure of group with better mechanical properties was analyzed. The results show that when the replacement rate of gold tailing composite sand is lower than 50%(mass fraction), the composite sand has better gradation. When the replacement rate of gold tailing composite sand increases from 0% to 50%(mass fraction), it is necessary to adjust admixture amount to ensure the good workability of gold tailing composite sand concrete. When the replacement rate of gold tailing composite sand is 20%~30%(mass fraction), the compressive strength, carbonization resistance and freezing resistance of C30~C50 concrete at different ages are significantly improved compared with the reference group without gold tailing composite sand, and the interweaving microstructure hydration products enhances the structural compactness.