Abstract: The use of modified fly ash absorbing the methyl orange of laboratorial wastewater has been studied.The modified fly ash was prepared when the concentration of hydrochloric acid was 2.0 mol /L,modified temperature was at 25 ℃ and acid division modification of fly ash was 1∶3.The results show that,the absorption rate of methyl orange was about 98 % when the amount of fly ash was 50 g/L and pH value was 4 at the temperature of 30 ℃.The effects was favorable and the absorption rate of methyl orange can still reach to about 95% when using the regenerative modification fly ash which was prepared by the 0.1 mol /L aluminum sulfale