TheatomicscalecomputersimulationforinitialprecipitationmechanismofNi75Al6V19alloywascarriedoutforthefirsttimebyemployingthemicroscopicdiffusionequation.Theinitialprecipitationprocesswasinvestigatedthroughsimulatingtheatomicpicturesandcalculatingtheorderparametersofthetwokindsoforderedphases.Simulationresultsshowthattheγ′orderedphaseprecipitatedearlierthanθorderedphasebycongruentordering+spinodaldecompositionmechanismandthusproducedanonstoicheometricγ′singleorderedphase.Then,thenonstoichiometricθphaseprecipitatedbyanon-classicalnucleationandgrowthmechanismattheAPBSofγ′phase.