The magnetic susceptibilities F of liquid Dy-Co and Er-Co alloys have a large and negative temperature coefficient, which suggests that the Dy, Er, and Co ions in their liquid alloys are in the magnetic state. However, the temperature dependence of F in both systems becomes weak near the content of 70 at% Co. It is interesting that the compositional dependence of F for liquid Dy-Co and Er-Co alloys has a minimum at content of 80 at% Co, respectively. On the Co-rich side, the magnetic susceptibility of liquid Dy-Co and Er-Co alloys obeyed the Curie-Weiss law with regard to their temperature dependence of F. On the rare earth-rich side, the magnetic susceptibilities of liquid Dy-Co and Er-Co alloys also exhibited Curie behavior with a reasonable value for the effective number of Bohr magnetons. The compositional dependence of F 4f for liquid Dy-Co and ErCo alloys was extracted by subtracting the corresponding data for liquid La-Co alloys from F for the liquid Dy-Co and Er-Co alloys, respectively.