Test pieces of 2002 duplex stainless steel composed of different proportion of phases with various amount of alloying elements were prepared by solution treatment. The effect of microstructure partition on the pitting initiation and propagation of the steel in 3.5% (mass fraction) NaCl solution were investigated by means of potentiostatic polarization, potentiodynamic scanning and surface morphology analysis. Results show that with the increase of solution treatment temperature, the main alloying elements gather to γ phase, the volume faction of α phase increases but the anti-corrosion property of the steel decreases, therewith, pitting initiates on α phase more easily. As a consequence, the pitting resistance of 2002 DSS decreases. The formed pits present lacework-like morphology, beneath the cover of a lacework there is a dish-lie pit with larger mouth opening but shallower depth. In a word, 2002 duplex stainless steel exhibits better corrosion resistance, which may be ascribed to that the formed pits on the steel surface tend preferentially to grow laterally but not deeply.