Polymer functional micro devices are widely applied in many important fields, which badly need polymer based micro/nano composites with high performances and multi-functions and realizing their micro injection molding processing. This is a rapidly developing frontier of modern science and technology. This paper briefly summarized our research work on preparation and micro injection molding processing of a series of polymer functional micro/nanocomposites by organic/inorganic hybrid, solid state shear milling, molecular complexation and melt compounding, e.g. nylon 11 (PA11)/barium titanate (BT) piezoelectric micro/nanocomposite, poly(vinyl alcohol) (PVA)/hydroxyapatite (HA) biomedical nanocomposite and thermoplastic polyurethane (TPU)/carbon nanotubes (CNTs) conductive composites. Keywords: polymer micro/nanocomposite; preparation; micro injection molding; micro device