  We present the semileptonic decay of $B_{c}$ meson in a QCD potential model
with the coulombic part of the Cornell potential $-\frac{4\alpha_{S}}{3r}+br+c$
as perturbation. Computing the slope and curvature of Isgur Wise function in
this approach, we study the pseudoscalar and vector form factors for the
transition of $B_{c}$ meson to its S wave charmonium $c\bar{c}$ states.
Numerical estimates of widths for the transitions of $B_{c}\rightarrow
J/\psi(\eta_{c})l\nu_{l}$ are presented. The results are found to be in good
agreement with other theoretical values.
