A high-performance AlCrTiSiN high-entropy alloy (HEA) nitride coating, consisting of a columnar CrN (BL-1), a nano-multilayered CrN/AlCrN (BL-2), a columnar AlCrN (TL) and a nano-multilayered AlCrTiSiN HEA nitride layer (HEA-NL) towards to surface, was isochronally annealed at 700 degrees C similar to 900 degrees C. Microstructural change and phase transformation of each individual layer of the HEA nitride coating were studied, as well as microstructureproperty relationship. Phase transformation sequence of CrN -> Cr2N -> Cr -> sigma-CrFe occurs in the BL-1 by nucleation and growth upon annealing, whereas the fcc-AlCrN solid solution of the BL-2 adopts a two-step phase transformation sequence: first to enriched-Al and enriched-Cr fcc-domains by interface-directed spinodal decomposition, and subsequently to hcp-AlN and sigma-CrFe by recrystallization, accompanied by the dissolution of layered structure and the diffusion of Fe deriving from steel substrate. The TL shows two different features from that of the BL-2: (i) there is a precipitation process of hcp-AlN from the fcc-AlCrN; (ii) the spinodal decomposition is isotropic spinodal decomposition. The HEA-NL shows drastic differences in spinodal decomposition behavior and microstructure compared to the TL, in which interface-directed spinodal decomposition produces a triple-layer consisting of a rich-Cr/Ti layer fcc-domains confined by two enriched-AlN ones, simultaneously resulting in a notable self-hardening. Subsequently recrystallization results in a aging softening at 900 degrees C due to the dissolution of nano-multilayered structure, the phase transformation of enriched-Al fcc-domain to hcp-AlN and the formation of soft Cr. Moreover, both Cr2N and s-phase layers deteriorate the adhesion strength.