To enhance the resistance to wear of Co matrix alloy as high-temperature hot-end parts, the Co-based composites reinforced by strontium sulfate (4.0, 9.0 and 14.0   wt.%) were prepared by using a powder metallurgy technology (P/M). The effects of SrSO4 on the microstructure, phase and tribological properties of composites were systematically investigated. The tribological behaviors of Co-based composites were tested from room temperature to 800  oC against Si3N4 ball by a ball-on-disk tribo-tester. The results indicated that SrSO4 decomposed during sintering, and the tribological properties of composites were improved by the addition of SrSO4. The composite with 9.0   wt.% SrSO4 had favorable tribological behavior, which was attributed to the in-situ synthesized solid lubricants and lubricating film formed on the contact surfaces.