  We study the rare decays $B^{+}_u\to \pi^{+}\ell^{+}\ell^{-}$,
$\rho^{+}\ell^{+}\ell^{-}$ and $B^{0}_d \to \ell^{+} \ell^{-}(\ell=e,\mu)$ in
the R-parity violating supersymmetric standard model. From the latest upper
limits of $\mathcal{B}(B^+_u\to\pi^+\ell^+\ell^-)$ and
$\mathcal{B}(B^0_d\to\ell^+\ell^-)$, we have derived new upper bounds on the
relevant R-parity violating couplings products, which are stronger than the
existing ones. Using the constrained parameter space, we present the R-parity
violating effects on the branching ratios and the forward-backward asymmetries
of these decays. We find that $\mathcal{B}(B^0_d\to \ell^+\ell^-)$ and
$\mathcal{B}(B^+_u \to\rho^+\ell^+\ell^-)$ could be enhanced several orders by
the R-parity violating sneutrino and squark exchanges, respectively. The
R-parity violating effects on the dilepton invariant mass spectra of $B^+_u\to
\pi^+\ell^+\ell^-$, $\rho^+\ell^+\ell^-$ and the normalized forward-backward
asymmetry $\mathcal{A}_{FB}(B^+_u\to\pi^+\ell^+\ell^-)$ and
$\mathcal{A}_{FB}(B^+_u \to\rho^+\ell^+\ell^-)$ are studied in detail. Our
results could be used to probe the R-parity violating effects and will
correlate with searches for the direct R-parity violating signals at the future
experiments.
