Fersmite, found in the Baiyunebo deposit, China, is a critical source of niobium. The flotation of synthesized fersmite has been studied using different collectors such as cycloalkyl hydroxamic acid, alkyl hydroxamic acid, benzylarsonic acid, styrylphosphonic acid, and diphosphonic acid. Out of all the collectors screened, the diphosphonic acid(DPA) is a particularly good collector and has a good selectivity in fersmite flotation. The interaction of fersmite with diphosphonic acid was studied by electrokinetic measurements, infrared spectroscopy and X-ray photoelectron spectroscopy analyses. Based on the results of electrokinetic potential measurements and the IRS and XPS analyses, a chemical adsorption mechanism of fersmite with DPA has been proposed. The flotation behavior of fersmite with this collector was consistent with the proposed mechanism and the distribution of diphosphonic species in aqueous solution as a function of pH.