<p>An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories. The effects of calcia-stabilized zirconia on the microstructure evolution and properties of magnesia–spinel refractories were characterized by the high-temperature elastic modulus, thermal shock damage resistance parameters, retainment of elastic modulus after thermal shock, and scanning electron microscopy. The results indicated that the incorporation of calcia-stabilized zirconia improved the thermomechanical properties and thermal shock behavior of magnesia–spinel specimens. The hot modulus of rupture of magnesia–spinel specimens increased by 2.5-fold due to the incorporation of calcia-stabilized zirconia micro-powder. The presence of a martensitic phase transformation in partially unstable ZrO₂ and thermal mismatches among various phases contributed to a controlled formation of microcracks. And the pinning effect caused by the calcia-stabilized zirconia particles surrounding the grain boundaries played a crucial role in preventing the propagation of microcracks. This phenomenon significantly bolstered the thermal shock stability of magnesia–spinel refractories, consequently prolonging their service life.</p>