The effect of poling on the switching properties of SrBi2Ta2O9 films was investigated via the technique of switching current testing. The samples with 660nm thickness were poled under dc voltage ranging from 1 to 8.25V, and for different duration from 1 to 80min. After poling, both the net-switched charge and switching time first jumped to higher values, then decreased with the elapse of time. The decreases were separated into two regimes, a fast and slow regime. The change of net-switched charge and switching time with poling voltage and poling time showed nonmonotonic behavior. These results were explained by the change of domain kinetics and the redistribution of charge carriers under both the applied and depolarization field.