To improve the bonding strength, the concept of functionally graded coating was applied in the joining of AlN ceramics to metals. Functionally graded Ti metallic coating was prepared by molten salt reaction. The coating thickness increased linearly with reaction temperature, time and initial K2TiF6 concentration. The disproportionation of Ti2+ was the rate-determining step of poly-step coating process and its activation energy was estimated to be 192.4 kJ/mol. The phases appeared in the coating were TiO, TiO1-x and TiN. The coating has a lamellar microstructure TiO/TiO1-x/TiN/TiN + AlN FGM interlayer. No obvious interface between AlN and coating was observed.