Metal magnetic memory technology was applied to the detection of rebar corrosion in concrete. The corrosion area could be located and the corrosion degree could be evaluated according to the change of the magnetic signal on the surface of the corrosion specimen.A series of experiments were implemented by using a self designed magnetic memory scanning equipment to acquire the magnetic signal of the corrosion specimen. Then, the By y，By z and zf y graphs which reflect the magnetic field distribution of the corrosion specimen can be obtained. The corrosion area could be located according to the position and distance of two intersecting points in the graph of By y. The corrosion degree can be semi quantitatively evaluated according to the zf value in the graph of zf y. It has been proved by these experiments that this technique has a high detection sensitivity to be able to effectively detect rebar corrosion before the concrete is not cracked. It can exclude the effect of concrete thickness on the detection.