A laminated structured 2205 duplex stainless steel (DSS) with graded grain size was prepared via aluminothermic reaction and subsequent hot rolling with deformation of 80% at 1000 degrees C, and its mechanical properties, strengthening and toughening mechanism were studied. Our materials have extraordinary elongation of 54% and high tensile strength of 990 MPa. The lamellar structure is characterized with heterogeneous lamella austenite (with nano-grain, ultrafine grain, micro-grain and nano-twin) and ferrite (with ultrafine grain and a proper amount of micro grain) coalesced alternately. The high strength is attributed to strengthening of complex grain (distribution from nanoscale to microscale) and interfaces arising from hierarchical and laminated dual-phase heterogeneous structure and distribution. The unusual high ductility is thought to be mainly attributed to the lamellar structure and dislocation hardening.