The flake particles in manufactured sand (MS) affects the properties of concrete. The effects of the size (1.18~2.36 mm, 2.36~4.75 mm, 4.75~9.50 mm) and the content (10%, 20%, 30%, both are mass fraction) of the flake particles on the fluidity and strength of mortar were studied, and the workability, compressive strength and electrical flux of the concrete prepared from the MS with different content of flake particles were measured. The interface microstructure and pore structure of the MS mortar with different content of flake particles were examined by scanning electron microscope and mercury porosimeter. The results show that with the increase of the content or size of flake particles, the flowability, strength and impermeability of the MS mortar and concrete gradually decrease, and the reduction of flexural strength affected by flake particles from the MS is higher than that of compressive strength. Compared with the regular particles, flake particles weaken the interface transition zone between cement paste and MS particles, and increase the porosity of the mortar and the proportion of large-sized and harmful pores, resulting in the performance degradation of mortar and concrete. Therefore, the content of flake particles in MS, especially the flake coarse sand particles, should be strictly limited.