The effects of a novel solidifying aid on the solidification of incinerated sludge ash were investigated in this study. The compressive strength and the heavy metal leaching toxicity of the solidification block were measured, and the composition and the microstructure were also detected by XRD and SEM. The results showed that the optimal solidifying agent was as follows: incinerated sewage sludge ash (ISSA): Portland cement: Kaolin: solidifying aid= 100:40:10: 0.7. The compressive strength of 12.74 MPa was observed when ISSA was mixed with the best solidification condition after 28 days curing. TCLP test results showed that the concentrations of all the metals in the leachate of the solidified samples are below those set in the maximum solubility limit issued by the Environmental Protection Agency in China. The XRD and SEM analysis indicated that the structure of the solidification block was of many acicular crystals and very dense. Furthermore, quartz, CaAl2Si2O8, Ca2Al2SiO7 and other materials could be found in the solidification blocks, which were known as improving the compressive strength of the solidification blocks.