Abstract Molecular models were established to predict the miscibility of polyimide/polythene mixing systems and the enhancing effects of compatibilizer addition of maleic anhydride grafted polythene (MAH-g-PE). Molecular dynamics simulations were applied to investigate radial distribution functions and Flory-Huggins parameters of the mixing systems. Results show that polyimide/polythene is miscible to a certain degree, and the miscibility gets better after adding MAH-g-PE. Dissipative particle dynamics (DPD) simulations display that micro-phase separation occurs in the polyimide/polythene mixing systems, however, effective interfaces appear between polyimide and polythene phases after adding MAH-g-PE. The results of molecular mechanics simulations indicate that the ability of mixing systems to resist stretch, compression and shear deformation increases after adding MAH-g-PE. This work offers a promising technique to predict miscibility properties for polyimide/polythene system prior to actual production and attempt to find a suitable compatibilizer for that system.