Abstract: Microstructure and oxide layer of new typed 12wt% Cr ferrite heat resistant steel after creep at 120 MPa, 650 ℃ was observed and analyzed by using electron probe, scanning electron microscope, and energy dispersion spectrometer. The results show that the creep process of the tested steel had three stages, and fractured at 3 980 h. The original martensitic laths in the tested steel disappeared after creep, while a lot of M23C6 phases grew and coarsened along the original austenite boundaries and the Fe2(W, Mo) intermetallic compound was found during the later time of creep. The oxide layer with three-layer structure was obtained on steel surface during creep, the inner layer oxide closing to the substrate was main Cr, Mn and Si elements, the mid-layer oxide was main Fe element and the out layer oxide was main Cr, Mn and Si elements.