<p>The second phase in S31254 super austenitic stainless steel precipitates easily, and the solution heat treatment can play an important role in its microstructure and properties. In this study, the effect of Ce on solidification microstructure evolution, elemental segregation, inclusions, and second-phase precipitation in S31254 super austenitic stainless steel was systematically studied. The samples with different Ce contents were solution-treated under the conditions of different time and temperature. The precipitated phases and corrosion resistance in stainless steel after solution heat treatment at different temperatures were further investigated by microstructure analysis and electrochemical experiments. The results showed that the samples needed to be solution-treated at temperatures above 1150&#xa0;°C, and the solution temperature affected the dissolution rate of the precipitated phases more than the change of Ce content. According to the grain size, microstructure, and precipitation of the second phase, the sample solution-treated at 1180&#xa0;°C for 60&#xa0;minutes had the best corrosion resistance among the studied samples as the <i>E</i>_corr and <i>E</i>_pit values for the 0.0095&#xa0;pct Ce sample increased by approximately 16 and 3.6&#xa0;pct compared to original sample without Ce addition; this condition might be a more suitable solution parameter. The improved corrosion resistance can be explained by the fact that the precipitation phase was all dissolved, and the sample had a proper grain size and contained a greater number of twins in the structure. A proper amount of Ce (0.0095&#xa0;pct) addition can not only refine the dendrite microstructure and second phase but also improve the corrosion resistance of steel. This provides theoretical guidance in optimizing the heat treatment process for rare-earth-treated super austenitic stainless steel.</p>