309L is a kind of austenitic stainless steel.This paper discusses 309L,which was smelted and rolled in a lab.Its microstructural characteristics in states of as-cast,hot-rolling,cold-rolling and solid solution were investigated respectively by optical microscope (OM).It is found that 309L is composed of austenite and residual δ-ferrite under these conditions,and the δ-ferrite cannot be eliminated easily by heat-treatment.Its hot plasticity and deformation resistance were investigated in a series of heat simulation tests.Its mechanical properties under different cold reductions were studied.All these provide valuable experimental data for the industrial production.