In this study, the selective adsorption of (1-hydroxyethylidene) bis-phosphonic acid tetrasodium salt(HEDP-4Na) on a calcite surface and its impact on the separation of brucite were examined using amicroflotation test, contact angle measurement, zeta potential measurement, X-ray photoelectron spectroscopy(XPS), and atomic force microscopy (AFM). The microflotation test revealed that HEDP-4Naselectively inhibited calcite from brucite at pH 10.5 in the sodium dodecyl sulfonate (SDS) system. Under the dosage condition of 180-mg/L HEDP-4Na, a single-mineral floating difference of 73.79% wasachieved between brucite and calcite. The contact angle measurement revealed that HEDP-4Na considerablyreduced the contact angle of calcite in the SDS system but only weakly affected the contact angleof brucite. Zeta potential analysis and Fourier transform infrared spectroscopy demonstrated that theHEDP-4Na adsorption interfered with the SDS adsorption on the surface of calcite; however, theHEDP-4Na adsorption had little effect on the SDS adsorption on the surface of brucite. XPS and AFM analysesdemonstrated that the selectivity and effect of HEDP-4Na on calcite were considerably stronger thanthose on brucite and the HEDP-4Na adsorption on the calcite surface was significant and strong.