  Within the constituent quark model, we examine the extent to which the
deuteron photo-disintegration at 2-6 GeV can be described by the quark-exchange
mechanism. With the parameters constrained by the $np$ scattering, the
calculated differential cross sections disagree with the data in both magnitude
and energy-dependence. The results can be improved if we use a smaller size
parameter for quark wavefunctions. We also find that the on-shell approximation
used in a previous investigation is not accurate
