  The ${\Upsilon}(nS)$ ${\to}$ $B_{c}D_{s}$, $B_{c}D_{d}$ weak decays are
studied with the pQCD approach firstly. It is found that branching ratios
${\cal B}r({\Upsilon}(nS){\to}B_{c}D_{s})$ ${\sim}$ ${\cal O}(10^{-10})$ and
${\cal B}r({\Upsilon}(nS){\to}B_{c}D_{d})$ ${\sim}$ ${\cal O}(10^{-11})$, which
might be measurable in the future experiments.
