A series of Ca₉NaZn(PO₄)₇: Eu²⁺/Eu³⁺, Tb³⁺ (CNZP: Eu²⁺/Eu³⁺, Tb³⁺) phosphors were synthesized by the solid-state reaction method. The results of structure refinement indicate that the chemical formula of CNZP can be written as Ca_9.12(5)Zn_0.88(5)Na_1.0(2)(PO₄)₇. Ca²⁺ ions fully occupy M1 site and partly occupy M2, M3 and M5 sites. The M4 sites are 100% occupied by Na⁺ ions and Na⁺ ions didn't participate in other sites. Zn²⁺ ions partly occupy M2, M3 and M5 sites and the biggest occupation 81(2)% of Zn²⁺ was observed for M5 sites. There are both 6-coordinated and 8-corrdinated Ca²⁺ and Zn²⁺ in CNZP matrix. According to Davolos's theory, we speculated that Eu³⁺ ions could substitute both Ca²⁺ and Zn²⁺ ions in CNZP matrix, while Eu²⁺ ions could only replace Ca²⁺ ions but not Zn²⁺ ions in CNZP host. Eu³⁺ ions doped in CNZP matrix only partly were reduced to Eu²⁺ state under the preparation conditions. The reaction mechanism was proposed. The emission color of the as-prepared phosphor were tuned from blush-violet to warm-white and yellowish-green by energy transfer of Eu²⁺→Tb³⁺ and Tb³⁺→Eu³⁺ in CNZP: Eu²⁺/Eu³⁺, Tb³⁺ phosphor. The samples showed good thermal stability. All the results imply that CNZP: Eu²⁺/Eu³⁺, Tb³⁺ phosphor is a potential color-tunable phosphor candidate for n-UV LEDs.