The infinite-layer (Sr 1- x Ca x ) 1- y CuO 2 has been synthesized in different atmospheres under high pressure. It was found that the alkaline-earth deficiency in (Sr 1- x Ca x ) 1- y CuO 2 has not been accommodated as cation vacancies on the (Sr, Ca) site of the infinite-layer phase as expected. This deficiency leads to CuO precipitation in the samples prepared in the inert atmosphere and formation of (Sr, Ca) 14Cu 24O 41 phase in the samples prepared in the oxidizing atmosphere. Superconductivity with T c(onset) = 60 K has been observed in the prepared samples. The oxidizing atmosphere becomes unfavorable to the superconductivity of the samples because of the appearance of the (Sr, Ca) 14Cu 24O 41 phase.