As modern aircraft engines advance towards higher thrust-to-weight ratios, increased reliability, and longer lifespans, greater demands are placed on the temperature-bearing capacity and comprehensive service performance of superalloys in hot-end components of engines. In the preparation process of cast superalloys, minor alloying elements in the master alloy play a crucial role in optimizing the microstructure and mechanical properties. This paper focuses on the extensively used K417 and K417G casting superalloys, analyzing the function mechanisms of typical minor element Zr and characterization methods of its distribution features. The analysis mainly includes the influence of minor element Zr on the solidification characteristics, microstructure, and stress-rupture life of casting superalloys. Research shows that the addition of Zr element can effectively reduce the liquidus and solidus temperatures of the alloy and promote the formation of eutectic structure. At the same time, the addition of an appropriate amount (mass fraction of 0.07%–0.09%) of Zr can help improve the stress-rupture life of K417G superalloys; In addition, the time-of-flight secondary-ion-mass-spectrometry and transmission electron microscopy analysis results show that the Zr element is distributed along the interface between the eutectics and alloy matrix in the form of Ni₁₁Zr₉ intermetallic compounds, instead of being only enriched at the grain boundaries as previously believed. The above research provides theoretical basis and data support for the control of minor alloying element content in cast superalloys.