  In this work, we calculated the branching ratios, polarization fractions and
CP asymmetry of decay modes $B\to\rho(\omega)\rho(\omega)$ in the Perturbative
QCD approach, which is based on $\mathbf{k}_T$ factorization. After
calculation, we find the the branching ratios of $B^0 \to \rho^+ \rho^-$, $B^+
\to \rho^+ \rho^0$ and $B^+ \to \rho^+ \omega$ are at the order of $10^{-5}$,
and their longitudinal polarization fractions are more than 90%. The above
results agree with BarBar's measurements. We also predict the branching ratios
and polarizations of $B^0 \to \rho^0 \rho^0$, $B^0 \to \rho^0 \omega$ and $B^0
\to \omega \omega$, which will be measured in future. We predicted the CP
asymmetry of $B^0 \to \rho^+ \rho^-$ and $B^+ \to \rho^+ \rho^0$, which will
play important role in determining angle $\alpha$.
