  We present a complete study of the $B\to
D^*P\ell^+\nu_\ell~(\ell=e,\mu,\tau)$ decays with the non-resonant, the charmed
axial vector resonant and the charmed tensor resonant contributions by using
the SU(3) flavor symmetry. Relevant amplitude relations between different decay
modes are obtained by the SU(3) flavor symmetry. We then predict non-measured
branching ratios of the $B\to D^*P\ell^+\nu_\ell$ decays with the non-resonant
and the charmed resonant contributions by using present experimental data of
the $B\to D^*P\ell'^+\nu_{\ell'}~(\ell'=e,\mu)$ decays within $2\sigma$ errors.
We have found that $B^{0,+}\to D^*\eta\ell^+\nu_\ell$, $B^{0,+}\to
D^*\eta'\ell^+\nu_\ell$, $B^{0}_s\to D^*_s \eta\ell^+\nu_\ell$, $B^{0}_s\to
D^*_s\eta'\ell^+\nu_\ell$ and $B^{0,+}\to D^{*}_sK\ell^+\nu_\ell$ decays only
receive non-resonant contributions. Decays $B^0_s\to
D_s^{*-}\pi^0\ell^+\nu_\ell$ only receive the $D'_{s1}$ resonant contributions.
Other decays receive all three kinds of contributions, and three kinds of
contributions are important in most of decays.
