  We present results of three-dimensional, fully nonlinear MHD simulations of a
large-scale magnetic field evolution in a barred galaxy. The model does not
take into consideration the dynamo process. We find that the obtained magnetic
field configurations are highly similar to the observed maps of the polarized
intensity of barred galaxies, because the modeled vectors form coherent
structures along the bar and spiral arms. Due to the dynamical influence of the
bar the gas forms spiral waves which go radially outward. Each spiral arm forms
the magnetic arm which stays much longer in the disk, than the gaseous spiral
structure. Additionally the modeled total energy of magnetic field grows due to
strong compression and shear of non-axisymmetrical bar flows and differential
rotation, respectively.
