  The dynamics of saxion in a supersymmetric axion model and its effect on the
axion production is studied in detail. We find that the axion production is
very efficient when the saxion oscillation amplitude is much larger than the
Peccei-Quinn scale, due to a spike-like behavior of the effective axion mass.
We also consider the axino production and several cosmological consequences.
The possibility of detection of gravitational waves from the non-linear
dynamics of the saxion and axion is discussed.
