The ordering of polarization field of inhomogeneous ferroelectric systems were investigated. We found that these systems exhibit rather complex polarization ordering behaviors with the coexistence of polar and toroidal ordering, and particularly, a novel and tunable polar-toroidal phase transformation under external mechanical, electrical or thermal fields. Accompanying with this polar-toroidal phase transformation, there is a large change of polarization and strain. As a result, large eletromechanical and thermomechanical performance can be achieved in these systems. The polar/toroidal phase boundaries can be regarded a new kind of morphotropic phase boundary (MPB). The polar-toroidal phase transformation in nanoscale ferroelectric systems should provide us a novel strategy to develop energy conversion nanodevices.