Cu⁺-containing calcium phosphate glasses have been prepared by remelting Cu-containing glass (a) under a controlled atmosphere of low oxygen pressure, and (b) with silicon powder as a reducing agent. About 96% of copper became cuprous ion by remelting under an oxygen partial pressure of 10^-10Pa at 1400°C for 8h. However, further reduction of oxygen pressure was not effective but led to the vaporization of phosphor, resulting in an increase in the devitrification tendency of the melt. Remelting with silicon powder was much more effective in reducing Cu²⁺ to Cu⁺ state. More than 99% of copper could be reduced to cuprous state by the remelting at 1250°C for 0.5h when the ratio of silicon to copper, Si/Cu, was equal to 2.5 or larger. The emission intensity from the Cu⁺-containing glass became maximum when Si/Cu=2.5.