Within the Standard Model, we investigate the semi-leptonic weak decays of $J/psi$. The various form factors of $J/psi$ transiting to a single charmed meson ($D^{(*)}_{(d,s)}$) are studied in the framework of the QCD sum rules. These form factors fully determine the rates of the weak semi-leptonic decays of $J/psi$ and provide valuable information about the non-perturbative QCD effects. Our results indicate that the decay rate of the semi-leptonic weak decay mode $J/psi to D^{(*)-}_{s}+e^{+}+ u_{e}$ is at order of $10^{-10}$.