To address the problem of severe pollution by acidic chromium-contaminated wastewater in mining areas, a novel adsorbent material known as nano-FeS loaded with fly ash (nFeS-F) was prepared by the ultrasonic precipitation method. Constructed with fly ash and nFeS-F as fillers, the dynamic columns 1# and 2# were employed to conduct dynamic treatment tests on acidic chromium-contaminated wastewater, after which the fly ash and nFeS-F were characterized by XRD, SEM, TEM, and XPS to investigate the regularity, long-term performance and removal mechanism of the fly ash and nFeS-F in treating acidic chromium-contaminated wastewater. The results showed that under the condition of influent Cr(Ⅵ) concentration of 100 mg/L, the average removal rates of Cr(Ⅵ) and total chromium of 1# column were 42.86% and 36.65%, and those of 2# column were 70.74% and 53.12%, respectively, within 28 days of operation of the columns. By the end of the test, the pH of 1# column and 2# column were 5.50 and 6.38, respectively. According to the XRD and XPS characterization of nFeS-F, Cr(Ⅵ) was reduced to Cr(Ⅲ) and subsequently immobilized on the surface of nFeS-F, manifesting as precipitates of hydroxide and sulfide. nFeS-F showed excellent adsorption performance for Cr(Ⅵ) in the test. These findings can provide some technical reference for the treatment of acidic chromium-contaminated wastewater.