The proper reuse and treatment Municipal solid waste incinerator fly ash is a is current a global concern. MSWI fly ashes possess a high concentration of SiO 2 , allowing them to be utilized as a raw material in the production of CSEB. This research looks into compressed stabilized earth blocks (CSEBs) that use municipal solid waste incinerator fly ash (MSWIFA) as an alternative to soil-sand mixture and sand. The experiment was divided into two phases: in the first, the effect of municipal solid waste incinerator fly ash on substituting soil-sand mix without affecting original performance, as well as resistance to sulfate attack, was emphasized. The effect of MSWIFA particle size and replacement ratio on replacing natural sand was then investigated. The analysis reveals that including MSWIFA into a soil-sand mixture considerably improved block performance, particularly under wetting-drying cycles and sulfate attack. MSWIFA particle size and replacement ratio have a significant influence on block strength and water absorption. Compressive and flexural strength are improved by the addition of 20% MSWIFA with a particle size of 0/4.75 mm. As a result, the research establishes a new investigation into the environmental recycling of MSWIFA in the context of the circular economy.