The coercivity of Sm2Co17-based permanent magnets at high operating temperature gradually increased with increasing Cu and Zr content, but decreased as the Fe content increased. The magnet Sm(Co0.7Fe0.1Cu0.16Zr0.04)6.7 that was studied had a room temperature intrinsic coercivity of about 30 kOe. For this magnet, the temperature coefficient of coercivity RT − 500 o C β and Hci at 500oC are -0.148%/oC and 8.6kOe. The magnet is composed mainly by 2:17R cell interior, 1:5 cell boundary phase, as well as 2:17H lamellar phase. There is a maze-like domain structure in the magnet. The HRXRD evidence shows that the phase transformation at high temperature leads to the degraded magnetic properties of the magnets.