  With the decay constants of $D$ and $D_s$ mesons measured in experiment
recently, we revisit the study of the bound states of quark and antiquark in
$B$ and $D$ mesons in the relativistic potential model. The relativistic bound
state wave equation is solved numerically. The masses, decay constants and wave
functions of $B$ and $D$ mesons are obtained. Both the masses and decay
constants obtained here can be consistent with the experimental data. The wave
functions can be used in the study of $B$ and $D$ meson decays.
