Abstract: Four experimental multi-component Ni-base superalloys were designed to investigate the influence of high Ru and high Cr on the microstructural stability at high temperature. These alloys were solution-treated and then aged at 800-1 100℃ for 10-1 300 h. The experimental results showed that no TCP phases were found in the Ru-free or Cr-free alloy after aging at 1 000℃ for 1 300 h. For the alloy with high level of Cr addition, TCP phases were observed to precipitate along grain boundaries and in dendrite cores after 20 h and 50 h at 1000℃, respectively; after aging at 1000℃ for 1000 h, no TCP phases were observed in the alloy with high levels of Cr and Ru additions. It is indicated that the high level of Cr addition promotes the precipitation of TCP phases, while high level of Ru addition efficiently lowers the propensity for the formation of TCP phases in the high Cr-containing alloy, and thus improve the microstructural stability.