By the substitution of Ca for Y, the holes are introduced into the insulating host material YBa2Cu3O6, and an insulator-to-metal transition, as well as superconductivity at 60K, is observed. The measurements of crystal structure, resistivity and ac susceptibility are performed, and the results indicate that the CuO planes with sufficient carrier concentration is the important condition for sustaining the high-Tc superconductivity.