A kind of coupling particle (TiB2@AlP) was synthesized to enhance nucleation efficiency of primary Si. The formation of TiB2@AlP was regarded as: P atoms gather on the interface of TiB2 by atom-by-atom adsorption, arranged to P and Al atoms thick. Driven by undercooling, the AlP crystal forms on the interface of TiB2. Density functional theory calculations further demonstrate that the adsorption phenomenon is thermodynamically favorable. The adsorbed P atoms trend on the Ti-terminated interface rather than B-terminated one. Additionally, refining tests on Al-45Si alloys indicate that TiB2@AlP particles display a higher refining efficiency than AlP alone.