The stable separation of P from metallurgical-grade silicon (MG-Si) was achieved by introducing a micro negative-pressure (MNP) environment with oxidative ladle refining. The average relative removal efficiency of P was increased from -1.9428% to 21.7638% with the introduction of MNP environment. During MNP oxidative ladle refining (MNPOLR), P was not enriched in slag and instead was separated via gas phase transfer. Despite the low boiling point of P and its highly saturated vapor pressure, the volatilization of P was controlled by gas diffusion during conventional oxidative ladle refining. The continuous separation of fume via MNPOLR weakened the diffusion resistance of P in the gas phase, efficiently separating P from MG-Si. Therefore, MNPOLR is an effective P separation technique that can be widely applied.