Abstract: Aerated concrete blocks were prepared from vanadium-titanium magnetite tailings after iron separation from Chengde.The fineness and addition effects of tailing on dry density and compressive strength of samples were studied.The phase compositions and microstructures of samples by tailing addition were analyzed by XRD and SEM,and the water absorption and water resistance of the products were tested.The results show that the content of-0.074 μm particles reaches to 90.23% after 20 min of milling.Increasing the tailing fineness enhances the density of samples,and the dry density and compressive strength of samples firstly increase and then decrease with increasing tailing addition.Under the condition of tailing（grinding for 20 min）∶cement∶lime∶gypsum = 60∶20∶15∶5,the obtained aerated concrete block has a compressive strength more than 4.0 MPa and a dry density less than 595 kg·m^-3,which meets requirement of A4.5 grade of GB11968—2006 standard.XRD and SEM analysis show that adding 40%～60% tailing is beneficial to the formation of C-S-H gel and tobermorite,endowing the product with high strength,good water absorption and water resistance.