Taguchi's L8 experimental design was firstly applied to identify critical parameters affecting the efficiency of bridge formation between confluent and fresh microcarriers in bead-to-bead transfer of Vero cells. Statistical analysis indicated that stirring time, rest time and the interactions between stirring time and rest time, stirring speed and rest time had significant effects. Subsequently, a two-stage cell transfer process was performed successfully, in which an efficiency of bridge formation (15.3 +/- 1.7%) obtained from 8 h intermittent agitation made percentage of bare microcarriers decrease quickly from 66.7% to 2.0 +/- 0.8%.