  The pre-neutron-emission mass distributions for reaction $^{232}$Th(n, f) up
to 60 MeV are systematically studied with an empirical fission potential model.
The energy dependences of the peaks and valleys of the pre-neutron-emission
mass distributions are described by the exponential expressions based on the
newly measured data. The energy dependence of evaporation neutrons before
scission, which plays a crucial role for the reasonable description of the mass
distribution, is also considered. Both the double-humped and triple-humped
shape of the measured pre-neutron-emission mass distributions for reaction
$^{232}$Th(n, f) are reasonably well reproduced at incident energies up to 60
MeV. The mass distributions at unmeasured energies and the critical energies at
which the humped pre-neutron-emission mass distributions are transformed into
each other are also predicted.
