With Miyi diatomite as the carrier and ferric nitrate as the modification agent, nano-micron vanadium adsorbent was prepared in the study. Then the adsorption properties of the prepared adsorbent were characterized by XRD, XRF, SEM, and ICP-OES analysis. The effects of adsorption time, initial pH value and initial vanadium concentration on VO3− adsorption performance were studied and the adsorption mechanism was discussed. The adsorption of VO3− on Miyi diatomite was significantly improved by the modification with ferric nitrate. The adsorption process of VO3− on nano-micron vanadium adsorbent was in accordance with Langmuir isothermal equation and quasi-second-order kinetic model. The saturated adsorption capacity was 43.38 mg/g. The adsorption capacity was higher in the weak acid environment and peaked at pH = 4.