  We present a functional Schr\"{o}dinger picture formalism of the
(1+1)-dimensional $O(N) $ nonlinear sigma model. The energy density has been
calculated to two-loop order using the wave functional of a gaussian form, and
from which the nonperturbative mass gap of the boson fields has been obtained.
The functional Schr\"{o}dinger picture approach combined with the variational
technique is shownto describe the characteristics of the ground state of the
nonlinear sigma model in a transparent way.
