Abstract: A brief introduction to the hot topic of atomic-molecular double ionization irradiated by an ultra-short intense laser field is presented. A semi-classical model is proposed to account for the complex dynamics of molecular double ionization. With this model, we reproduce the experimental data over a wide range of laser intensities and reveal the significant influence of molecular alignment on double ionization yield. Back analysis on the double-ionization trajectories provides an intuitive way towards understanding the complex dynamics involved in molecular double ionization.