Coarse columnar crystals significantly contribute to the reduced mechanical properties and pronounced anisotropy observed in as-cast medium entropy alloys (MEAs), such as NiCoFe. Grain refinement is recognized as an effective strategy to mitigate this issue. The combined addition of interactive microalloying elements typically achieves greater refinement effects compared to the use of individual alloying elements. However, a precise predictive model for evaluating the grain refinement efficiency of multi-element microalloying remains lacking. This study investigates the influence of Ti and C additions on the grain refinement behavior of the NiCoFe MEA. The results indicate that the average grain size is effectively reduced from approximately 557 μm in the baseline alloy (NiCoFe MEA) to approximately 118 μm in the modified alloy ((NiCoFe)98.0Ti1.0C1.0 MEA). To quantitatively assess the refinement effects of these alloying elements, the growth restriction parameter β and the growth restriction factor Q were introduced. A predictive model expressed as [[EQUATION]]Keywords: Medium entropy alloy and Grain refinement and growth restriction parameter.