The material flow method and life cycle assessment method are combined to analyze the environmental impact of three disposal scenarios, including incinerated sewage sludge ash (ISSA) to landfill, ISSA substitution for clay, phosphorus recovery from ISSA then residue substitution for clay. The cost-benefit method compares the economic benefits of the three disposal scenarios. The results show that ISSA utilization is superior to ISSA to landfill in solving the problems of abiotic resource depletion, acidification potential, eutrophication potential, freshwater aquatic ecotoxicity, global warming potential, photo hem ozone creation potential. In addition, phosphorus recovery from ISSA then residue substitution for clay is the best disposal scenarios with a net income of 141.21 yuan/ton ISSA. If the disposal path is extended to all sewage treatment plants in China, 262,600 tons of phosphorus can be extracted and 2,092,300 tons of struvite can be produced each year.