  We performed Langevin dynamics simulations for the \textit{ac} driven flux
lines in a type II superconductor with random point-like pinning centers.
Scaling properties of flux-line velocity with respect to instantaneous driving
force of small frequency and around the critical \textit{dc} depinning force
are revealed successfully, which provides precise estimates on dynamic critical
exponents. From the scaling function we derive a creep law associated with the
activation by the regular shaking. The effective energy barrier vanishes at the
critical dc depinning point in a square-root way when the instantaneous driving
force increases. The frequency plays a similar role of temperature in
conventional creep motions, but in a nontrivial way governed by the critical
exponents. We have also performed systematic finite-size scaling analysis for
flux-line velocity in transient processes with \textit{dc} driving, which
provide estimates on critical exponents in good agreement with those derived
with ac driving. The scaling law is checked successfully.
