The spin reversal of nanostructured Co/Pd multilayers by varying the number of repeats has been investigated quantitatively. The magnetization viscosity measurement and the direct observation of the time-dependent spin reversal patterns showed that their reversal behavior gradually changed from wall-motion dominant to nucleation dominant by increasing the number of repeats. Both the wall-motion speed V and the nucleation rate R of the samples were determined by a quantitative analysis of the time-dependent domain patterns. It was found that V was significantly decreased and R was increased by increasing the number of repeats, and the ratio of V/R was an important parameter of different spin reversal behavior. (C) 1999 American Institute of Physics. [S0021-8979(99)28108-X].