  The light-front quark model has been successful in describing various meson
properties. We apply the model to the meson weak decays and discuss the
covariance of the model. We find that the inclusion of the higher-Fock
state(i.e. nonvalence or so called Z-graph) contributions is necessary to
recover the covariance of the light-front quark model. We present the
possibility of the effective calculation of the higher-Fock state contributions
to restore the covarince in the light-front model.
