At present, the problem of pollution and re-pollution caused by sewage sludge stacking at random has become increasingly serious in many regions and countries including China, which requires and stimulates researchers to explore more industrially feasible options to reduce environmental and eco-economic problems related to the current sludge management. In this work, an ultra-lightweight and eco-friendly ceramic (UEC) was synthesized from waste sewage sludge (SS) and kaolin clay (KC). By changing proportion of SS to KC, the mineral species, structure evolution, physical-mechanical properties, heavy metal risk assessment and sintering mechanism of UEC specimens were investigated. The results showed that the change of SS content did not vary the mineral species of UEC specimens, which all contained five mineral components: mullite (Al6Si2O13), sillimanite (Al2SiO5), hematite (Fe2O3), cristobalite (tetragonal SiO2) and aluminum iron phosphate (Al0.67Fe0.33(PO4)), but influenced their structure and performance. As the SS content increased from 20 to 50 wt%, the UEC specimen structure became denser and the inner pores grew continuously due to the increase of gas and glassy liquid phase. Meanwhile, the linear shrinkage, mass loss and bulk density also increased continuously, with corresponding maximum values of 18.59%, 30.45% and 1.92 g/cm3, respectively. Whereas the apparent porosity decreased significantly, and its value varied from 39.32% to 17.50%. Among all UEC specimens, the UEC-30 (SS/KC=30/70) and UEC-40 (SS/KC=40/60) had the most promising compressive strength (120 MPa) and bending strength (66 MPa), respectively. Also, the heavy metal leaching results of UEC specimens revealed that the final developed ceramic products were safe and non-toxic.