The effects of BaCl2 on the flotation of K-feldspar using dodecyl amine chloride as the collector under natural pH were investigated by flotation tests, absorption measurements, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results indicated that lower BaCl2 concentration can increase the floatability of K-feldspar, whereas higher BaCl2 concentration can significantly inhibit the flotation of K-feldspar. Peaks at 3548.18, 3475.56 and 3414.35 cm−1 in the FTIR spectra of K-feldspar adsorbed by dodecyl amine chloride revealed three forms of —OH. XPS analyses of K-feldspar adsorbed by Ba2+ showed that the concentration of K atom was reduced by nearly twice as those of Si, Al, and O. The activation of BaCl2 at a low concentration was mainly caused by Ba2+ in the form of the ion exchange between K+ and Ba2+. The inhibitory action of BaCl2 at a high concentration is mainly attributed to the physical absorption of Ba2+ on the surface of K-feldspar and the fact that a high concentration of Cl− causes the chemical equilibrium of dodecyl amine chloride to be changed, and the dodecyl amine chloride in the form of RNH2H+ is reduced.