  We study the contributions of the kaon pair originating from the resonance
$\rho(770)$ for the three-body decays $B \to D K\bar{K}$ by employing the
perturbative QCD approach. According to the predictions in this work, the
contributions from the intermediate state $\rho(770)^0 $ are relatively small
for the three-body decays such as $B^0 \to \bar{D}^0 K^+ K^-$, $B_s^0 \to
\bar{D}^0 K^+ K^-$, and $B^+ \to D_s^+ K^+K^-$, while about $20\%$ of the total
three-body branching fraction for $B^+ \to \bar{D}^0 K^+ \bar{K}^0$ could
possibly come from the subprocess $\rho(770)^+\to K^+ \bar{K}^0$. We also
estimate the branching fractions for $\rho(770)^\pm$ decay into the kaon pair
to be about $1\%$, and that for the neutral $\rho(770)$ decay into $K^+K^-$ or
$K^0\bar{K}^0$ to be about $0.5\%$, which will be tested by future experiments.
