The variations of the \{\}\+\{27\}Al nuclear magnetic resonance (NMR) spectra of the aluminum\|copper powder mixtures after
different time of ball milling have been measured.By analyzing the \{\}\+\{27\}Al NMR spectra,the
mechanical alloying (MA) process has been investigated at microscopic level.\{\}\+\{27\}Al Knight shifts in the series of Cu\|Al samples decrease with increasing time of ball\|milling.This means that the s component in the states of valence electron declines.The experimental results indicate that the ture alloying reaction takes place during the MA process,and it is complete after about 90 hours of ball milling under our mechanical alloying conditions.Compared with the early results of \{\}\+\{27\}Al Knight shifts measured in the samples prepared by the traditional melt\|alloying method,it has been concluded that the real Cu\|Al alloys can be
obtained by MA process,and they possess the same chemical short\|ranged order as those with the same ingredients obtained by melting.