Apatite is widely used as an inorganic non-metallic material, a geological indicator mineral, and a common gemstone variety. The chemical formula for apatite is［Ca₁₀(PO₄)₆(F, Cl, OH)₂］, Ca²⁺ sites can be isomorphously substituted by divalent transition metal cations (Fe²⁺, Mn²⁺, etc. ), rare earth element ions (La³⁺, Ce³⁺, Gd³⁺, etc. ), or alkali and alkaline earth metal ions (K⁺, Na⁺, Sr²⁺, etc. ), resulting in various colors such as yellow, green, blue, purple, and photochromic effects. Green fluor-hydroxyapatite turns into a bright blue hue after heat treatment at 650～700 ℃, possessing high ornamental and commercial value. The results show that the samplesare mainly composed of Ca²⁺ and P⁵⁺ with a small amount of N⁵⁺, which is mainly substituted［PO₃］in the form of —NH₂, indicating biochemical behavior correlated in formation. UV-Vis results show that the sample's color is mainly caused by the isomorphic substitution of Ce³⁺ and Mn²⁺ in the distorted octahedron of Ca²⁺, forming a blue-green transmission window. The defects in the green apatite sample before heat treatment are mainly ionic centers F^--O^--F^-, combining with O^2--O^--V and OH^--O^--V, caused by the isomorphic substitution of Ce³⁺ at the CaⅠ site. After heat treatment, the recovery of hole centers is mainly manifested as ionic center defects caused by Mn²⁺ substituting the distorted octahedron at CaⅠ and CaⅡ sites. Combining EPR spectra shows that Mn²⁺ can be distributed at both CaⅠ and CaⅡ positions, causing a blue hue in the samples; otherwise, when Ce³⁺ is highly substituted at the CaⅠ position, the samples turn green.