This study investigated the complex evolution of precipitates during the solidification of high-carbon nickel-based superalloy ingots, exploring the relationship between phase transformation and hot cracking sensitivity during solidification. The causes of hot crack sensitivity in ingots were identified using optical microscopy, scanning electron microscopy, and thermodynamic calculations. Differential scanning calorimetry and isothermal solidification experiments, combined with various structural analysis methods, were used to reveal the impact of phase transitions on hot crack sensitivity during solidification. The essence of high hot crack sensitivity due to the evolution of alloy solidification structure and its impact on mechanical properties were elucidated through zero-strength and zero-plasticity tests during solidification, along with thermal stress analysis. The solidification of the alloy produced complex precipitate phases. The significant enrichment of elements like Al, C, Ti, Co, Ni, Nb, and Mo in the liquid phase resulted in the formation of Laves phase and (γ+γ′) eutectic phase at lower temperatures. This led to a slower rate during the final stage of solidification, with a solidification temperature range of up to 151 °C. The first principal stress experienced by ingots in the brittleness temperature range was influenced by the ingot size and casting process. The stress often exceeded the strength limit of the alloy, indicating a high tendency for hot crack in the alloy. This revealed the relationship between the solidification process of superalloy and the toughness and strength of the ingot, providing theoretical and practical guidance for controlling the tendency to crack during solidification.