The aim of this article is to investigate the effect of Fe₂O₃ contents on the characteristics of lightweight aggregate that is made from sewage sludge and river sediment. The physical characteristics, compressive strength, morphological structures and crystalline phases of lightweight aggregate were studied, and the results showed that the lightweight aggregate with higher bulk density, higher apparent density, and lower water absorption could be obtained at Fe₂O₃ contents between 3.5％-7％. The SEM analysis points out that the surface of lightweight aggregate exhibits more vitrification phenomenon as the Fe₂O₃ contents increase, the dense surface of lightweight aggregate with evenly distributed micro porous can be found at Fe₂O₃ contents=5％. The lightweight aggregate with stronger compressive strength (more than 14 MPa) can be obtained when Fe₂O₃ contents are between 3.5％-7％. The XRD analysis implies that the main crystal phase in the lightweight aggregate are quartz, albite-anorthite, kyanite and hematite, and the silicate crystals with stable structure are the main crystal in the internal of lightweight aggregate. As the Fe₂O₃ contents increase, more Fe₂O₃ will transform to hematite with crystal structure. The results indicate that the Fe₂O₃ contents between 3.5％-7％ are appropriate in the process of making lightweight aggregate from sewage sludge and river sediment.