The aging behavior of Ni-Cr-Al ternary alloy are studied at temperature 1123 K, the early ordering process are simulated at atomic-scale with microscopic phase-field model. Precipitation mechanism of low supersaturated alloy Ni-15at.%Cr-10.5at.%Al is non-classical nucleation and growth, the precipitation process include three stages, i.e. the nucleation and growth of D022 ordering phase, nucleation of L12 ordering phase and transmit of L12 ordering phase from D022 ordering phase. The occupation possibilities of Al and Cr in L12 ordering phase are similar because of substitution behavior of Cr atom, Ni3(CrxAl1-x) structure are formed and coexist with D022 ordering phase. high supersaturated alloys show the congruent ordering and spinodal decomposition mechanism and the process of the ordering and clustering are precedent to low supersaturated alloys.