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In this study, modified coal fly ash (NMFA) was prepared by sodium hydroxide (NaOH) with low-temperature hydrothermal method. The differences of the ash to alkali mass ratio (5:3, 5:4, 5:5, 5:6), calcination temperature (100 ℃, 200 ℃, 300 ℃), and calcination time (1 h, 3 h, 5 h) were investigated. The adsorption experiments obtained the optimal result with the ash to base ratio of 5:5, calcination temperature of 200 ℃, and calcination time of 3 h, adsorbing 90.27 mg/g of Cd2+. The characterization results (SEM-EDS, FTIR, XRD, and XPS) also confirmed the effective adsorption of Cd2+ by NMFA. The functional groups of Si-O, Al-O, and Fe-O played an important role in Cd2+ removal. Meanwhile, the influences of dosage, different pH, and co-existing cations were also investigated. Quasi-secondary adsorption kinetics and Langmuir isotherm model were also referred to the Cd2+ adsorption by NMFA. Therefore, the good adsorption of NMFA-3 on Cd2+ provided new ideas for the safe utilization of fly ash and heavy metal purification in wastewater.