Despite great advantages of chitin for water purification, current researches have lacked the intensive study for the utilization of chitin in high-flux filters. To tackle this, we proposed, for the first time, a facile method for the construction of multifunctional nanoporous chitin ultrafiltration membranes derived from renewable marine resources (shells of shrimp and crab). Chitin nanocrystals with average diameter and length of 43.3 and 446.1 nm were prepared by H₂SO₄ hydrolysis, and a simple vacuum-filtration method was utilized to convert these uniform dispersed nanocrystals to nanoporous membranes. To greatly improve the permeation flux and functionality of the filtration membranes, a bioinspired dopamine coating procedure was adopted to intercalate high content silver nanoparticles (57.2 wt %) into the chitin nanocrystal matrix, which might construct interfacial regions and foster low-resistance channels for enhancing solvent permeability. The resulting hybrid chitin membranes possessed numerous interconnected nanopores and its thickness could be easily tuned from 100 to 4000 nm by the volume of filtered nanocrystal suspensions. They allow fast permeation of water during vacuum assisted filtration. Typically, the flux of 100 nm thick hybrid filtration membranes with ~4 nm cutoff was up to 13400 L m ⁻² h ⁻¹ bar ⁻¹, which was nearly 3 orders of magnitude higher than that of commercial filtration membranes. More importantly, the hybridization of Ag nanoparticles also offered the membranes with continuous flow properties, for example, super catalytic activity and substitution reactivity in decomposing toxic organic pollutants and recycling noble Au ions in water.