  We analyze the quasi-two-body decays $B^+\to\pi^+\rho(770,1450)^0 \to\pi^+
K^+K^-$ in the perturbative QCD approach. The results in this work do not
support that large branching fractions contributed by the resonances
$\rho(770,1450)^0$ in the $B^\pm \to \pi^\pm K^+K^-$ decays. The virtual
contribution for $K^+K^-$ from the tail of the resonance $\rho(770)^0$ which
has been ignored in the experimental studies is about $1.5$ times of the
$\rho(1450)^0 \to K^+K^-$ contribution, with the predicted branching fractions
${\mathcal B}_v=(1.31\pm0.27)\times10^{-7}$ and ${\mathcal
B}=(8.96\pm2.61)\times10^{-8}$, respectively, for these two subprocesses in the
$B^\pm \to \pi^\pm K^+K^-$ decays. The absence of $\rho(770)^0\to K^+K^-$ for
the decay amplitude of a three-body hadronic $B$ decay involving charged kaon
pair could probably result in a larger proportion for the contribution from the
resonance $\rho(1450)^0$ in the experimental analysis.
