Abstract: To optimize the vanadium extraction process in a sulfuric acid system and improve the recovery efficiency of vanadium resources, this study investigated the hydrolysis behavior, existing forms, and influencing factors of V(Ⅳ) and V(Ⅴ) ions in the sulfuric acid system by combining thermodynamic equilibrium systems. It separately plotted the species distribution diagrams of 0.02 mol/L V(Ⅳ) and V(Ⅴ) ions at 25 ℃. In conjunction with the characteristics of the roasting-free pressure acid leaching process, using di(2-ethylhexyl) phosphate (P204) as the extractant and self-made sulfonated kerosene as the diluent, the study systematically examined the effects of initial aqueous pH value, P204 dosage, extraction phase ratio (O/A), and oscillation time on the extraction performance of V(Ⅳ) and V(Ⅴ). The results showed that the existing form of vanadium in aqueous solution is mainly regulated by pH value and its own concentration. In the sulfuric acid system with pH < 3, V(Ⅳ) and V(Ⅴ) mainly exist in the forms of VO²⁺ and VO₂⁺, respectively. The extraction performance of P204 for V(Ⅳ) is significantly better than that for V(Ⅴ). The optimal extraction conditions for V(Ⅴ) are as follows: initial aqueous pH = 2.4, organic phase containing 20% P204, extraction phase ratio (O/A) = 1∶1, and oscillation time of 8 min. At these conditions, the extraction rate of V(Ⅴ) reaches 88.41%, while the extraction rate of V(Ⅳ) is as high as 96.39% at the same conditions. In the non-roasting pressure acid leaching process, pre-reducing V(Ⅴ) in the leaching solution to V(Ⅳ) can effectively enhance the total vanadium extraction efficiency.