Humic acid extraction from carbonaceous pressure-oxidized gold ore was carried out. The structure of humic acid was analyzed utilizing elemental analysis, FTIR, UV–Vis, Raman spectra and XPS. Also, the kinetic and isotherm models of the gold-adsorbing process were established to calculate the thermodynamic parameters and isosteric heat of adsorption. The results showed that affected by pressure oxidation, the aliphatic structure, C=O and other oxygen-containing groups were destroyed. Most importantly, new bonds, such as C—O—Clx, C—Clx and Me4N—Cl, were formed in the humic acid extracted from pressure-oxidized gold ore. The adsorption test results showed that, pressure oxidation made a profound impact on the gold-adsorbing performance of humic acid. The adsorption rate of humic acid decreased to (42.78±1.05)% for the pure gold solution and (28.63±1.11)% for the gold leaching solution after pressure oxidation. Adsorption findings conformed to the pseudo-second-order and Langmuir isotherm models. The isosteric adsorption heat of humic acid increased with the increase of the adsorption amount.