Abstract: Froth flotation is an effective method of quartz and feldspar separation. The development of highly selective reagents for separating feldspar from quartz has thus emerged as a research hotspot. In this study, an eco-friendly tannic acid (TA) was employed as a depressant to delve into its selective depressive effect on feldspar via meticulously designed pure mineral flotation tests and artificially mixed ore separation experiments. Its underlying mechanisms were investigated using such characterization techniques as Zeta potential, contact angle analysis, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Results reveal that under weakly acidic conditions, mixed ore flotation concentrates exhibited a quartz recovery rate of 92.79 %, with a selectivity index (SI) of 7.20, indicating effective separation of feldspar and quartz. The hydrophilic —OH groups of TA form coordinate bonds with Al³⁺ sites on feldspar surfaces. This impedes the adsorption of polyether amine (PEA) collectors onto feldspar via steric hindrance effects, thereby achieving the selective depression of feldspar. Therefore, in a weakly acidic system using PEA as the collector, TA serves as an effective depressant for achieving the flotation separation of quartz and feldspar.