  Schwinger pair production in some of space-dependent electromagnetic fields
is studied analytically by using worldline instantons formalism for scalar
quantum electrodynamics. With the increase of the modified Keldysh parameter
$\gamma_{keb}$, the pair production rate decreases, the region of instanton
paths expands regardless of the electromagnetic field form. We also find that
all of the paths of the instantons for various electromagnetic fields are
exactly in the same plane while with the different elliptical shapes. Moreover,
the magnitudes of the normalized instantons action with different external
electromagnetic fields are all bounded within the region from $\pi$ to $2\pi$
in spatial inhomogeneity fields. We further analytically identify and obtain
two kinds of the pair-production time associated to the worldline instantons
action.
