Herein, a novel nanocomposite organic solvent nanofiltration (OSN) membrane has been facilely fabricated by a highly-efficient one-step co-deposition of mussel-inspired catechol and octaammonium polyhedral oligomeric silsesquioxane (POSS-NH3+Cl-) onto supports. The basic properties and morphologies of the co-deposited nanocomposite membranes were investigated with various physicochemical characterizations in detail. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra proved the present of POSS nanoparticles on membrane surface. X-ray photoelectron (XPS) results suggested the optimal ratio of POSS-NH3+Cl- and catechol for co-deposition. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images demonstrated the formation of a layer on support surface. The optimized nanocomposite membrane exhibited an ethanol (EtOH) permeance of 1.26 Lm(-2) h(-1) bar(-1) with a rejection of 99% to Rose Bengal (RB). The novel membrane also exhibited remarkable separation performance for dyes removal from a wide range of solvents including challenging polar aprotic and strongly swelling solvents. Particularly, the nanocomposite membrane demonstrated stable performances during a two-day long term test in DMF for RB concentration. In addition to providing a highly-efficient way to high-performance OSN membrane, this work may stimulate the bio-inspired design of advanced nanocomposite membranes for environmental applications.