Fe-Cr slag is an industrial waste produced after using chromite as raw material to produce metal chromium and chromium salts.After wet detoxification by FeSO₄,the Fe-Cr slag still has certain volcanic ash activity,which can be used as concrete mineral admixture.However,the water-soluble Cr（Ⅵ） in wet detoxification of Fe-Cr slag affects the utilization of building materials resources.The particle size distribution and volcanic ash activity of the wet detoxification Fe-Cr slag were studied.The wet detoxification Fe-Cr slag was used as mineral admixture instead of fly ash in C30 concrete.The working properties,mechanical properties and leaching amount of water-soluble Cr（Ⅵ） of concrete were investigated.The results sho-wed that the particle size of the wet detoxification Fe-Cr slag was mainly distributed in the range of 1~20 μm,and the activity index of 28 d reached 68%.When the fly ash was replaced by 20% by the wet detoxification Fe-Cr slag,the slump of concrete increased by 38.2%,and the strength of concrete at 7 d and 28 d increased by 7% and 6%,respectively.The amount of water soluble Cr（Ⅵ） was different according to the different standard.Wet detoxification Fe-Cr slag may be used as mineral admix-ture,but the leaching of water-soluble Cr（Ⅵ） should be considered to ensure the safe use of concrete.