  We investigate the influence of the fourth generation quarks on the branching
ratio and the CP-asymmetry in B -->\pi \ell^+ \ell^- decay. Taking the
|V_{t'd}V_{t'b}| ~ 0.001 with phase about 10 degree, which is consistent with
the sin2\phi_1 of the CKM and the B_d mixing parameter \Delta m_{B_d}, we
obtain that for both muon and tau channels the branching ratio, the magnitude
of CP-asymmetry and lepton polarization depict strong dependency on the 4th
generation quarks mass and mixing parameters. These results can serve as a good
tool to search for new physics effects, precisely, to search for the fourth
generation quarks($t', b')$ via its indirect manifestations in loop diagrams.
