Jizhou kiln, one of the eight southern folk kilns of the Song Dynasty, is famous for its brilliant glaze colors. The traditional ceramic raw materials in Jingdezhen area were used to successfully realize the lead-free preparation of green glaze from Jizhou kiln with CuO as colorant, and the effect of CuO content on the color characteristics of copper glaze was also investigated. The results indicate that with the increase of CuO content, the viscosity of glaze layer gradually decreases, and the glaze surface shows light blue, green, dark green, and blue colors in sequence. Cu2+ is mainly green color, but the high concentration of Cu2+ as a glass modifier destroys the SiO2 network, increasing the amount of non-bridging oxygen and the density of oxygen ions around Cu2+, and the color of Cu2+ is mainly blue. After the addition of CuO, the samples exhibite circular and worm-like phase-separated structure. When the CuO content is higher, the smaller size of circular phase separation structure meets Rayleigh scattering, producing blue opalescence and deepening the glaze color. When the CuO content is lower, the larger size of circular phase separation structure satisfies Mie scattering and produces white milky light. The coloration mechanism of lead-free green glaze from Jizhou kiln results from the synergistic coupling effect of copper ion valence state and phase-separated structure.