<p>To provide a theoretical basis for optimizing the microstructure and mechanical properties of Co-based superalloy GH5188, the melting characteristic of VIM + ESR ingot, dissolution law of the carbides during homogenization, and the effect of homogenization treatment on mechanical properties have been investigated. The results show that incipient melting temperature of the ingot is 1260 ~ 1270 °C, and the low melting point phase is primary M₂₃C₆. In the homogenization process, the dissolution sequence of carbides was determined as follows: secondary M₂₃C₆ → primary M₂₃C₆ → primary M₆C. Interestingly, lots of small blocky and rod-like W-rich carbides precipitated during the dissolution of primary M₆C, but as the homogenization degree increased further, their precipitation was gradually inhibited. With the increasing homogenization time and temperature, the dendritic segregation reduced and the amount of residual carbides decreased gradually. The homogenization treatment of 1200 °C × 30h can completely dissolve the primary M₂₃C₆ and eliminate most of the small W-rich carbides, and the 1200 °C × 50h homogenization can eliminate majority of the carbides, minimize the segregation degrees of Cr, Co, and Ni, and significantly reduce that of W. Kinetic calculations indicate that the segregation of W can be completely eliminated after being homogenized at 1200 °C for about 59.3h. The room-temperature tensile properties of the alloy were not obviously influenced by the homogenization treatment. The high temperature hardness with homogenization treatment of 1200&#xa0;°C × 50h was the greatest, while the high-temperature stress rupture life was the longest with the homogenization treatment of 1200 °C × 10h. This indicates that the prolonged homogenization processing time may not always bring beneficial effects.</p>