Abstract: To remove the key impurity elements, P and B, from primary Si simultaneously, Sr and Zr co-addition to Al–Si alloy systems during solvent refining has been investigated. Sr reacts with Al, Si, and P in the melt to form a P-containing Al₂Si₂Sr phase and Zr reacts with B to form a ZrB₂ phase. In the Al–Si–Sr–Zr system, high removal fractions of P and B in the primary Si, with 84.8%–98.4% and 90.7%–96.7%, respectively, are achieved at the same time, respectively. The best removal effect is obtained in the sample with the addition of Sr-32000+Zr-3000 μg·kg^–1, and the removal fractions of P and B in the purified Si reach 98.4% and 96.1%. Compared with the Sr/Zr single-addition, the removal effects of Sr and Zr co-addition on P and B do not show a significant downward trend, indicating that the nucleation and growth of the B/P-containing impurity phases are mutually independent. Finally, an evolution model is proposed to describe the nucleation and the growth stages of Sr/Zr-containing compound phases, which reveals the interaction between the impurity phases and the primary Si.