To further understand the creep mechanism of γ′-strengthened Co-based superalloys under low temperature and high stress conditions. In this study, Co-Al-W- and CoNi-based single crystal superalloys were crept at 760 °C with high stresses according to their yield strengths, and the difference of deformation mechanisms for two types of superalloys was discussed. For the Co-Al-W-based single crystal superalloy, the creep curve can be divided into three stages, i.e., the deceleration stage, acceleration stage A and acceleration stage B. The creep behavior of CoNi-based single crystal superalloys is different from that of Co-Al-W-based single crystal superalloys by forming a second deceleration stage after the acceleration stage, which is similar as Ni-based single crystal superalloys. The Ni or Cr addition affect the deformation mechanism by formation of dislocation ribbons and APBs in the γ′ precipitate. The shearing of γ′ precipitates, either by the dislocation ribbon or single SF, decrease creep resistance. While the integration of SF interactions and APBs are more effective for improving creep resistance in CoNi-based superalloys than the SF interaction in Co-Al-W-based superalloys under low temperature and high stress conditions. This work will be significant for understanding the creep mechanism and alloy design strategy of γ′-strengthened Co-based superalloys.