The incineration of sludge is considered as one of the most common process in many landfill and municipal wastewater treatment sites. Incineration can reduce the sludge volume by eliminating the organic content and the potential energy can be utilized. The remaining materials after incineration are the nutrients and the inorganic material. Phosphorus is one of the most important nutrient that is resulting from incineration and it may be recovered by dissolving the leached incineration ash with one of concentrated acid. In this research paper the wasted of incinerated sludge ash that are resulting from municipal sludge incineration are used and then dissolved by nitric acid HNO₃ with different concentration and contact time. The results showed that the dissolving with nitric acid concentration of 30% or more than that with duration of 3 hours gives a percentage dissolving of phosphorus equal to 88.5% of the phosphorus that existing in sample. The process of phosphorus recovery from sludge incineration is very important process due to its economical benefits and to reduce the pollutants in the environment.