Abstract: The pure iron disk specimen and the standard carbon steels ball (45 steel) which constituted a ball-on-disk friction pair were used for the rotating friction test. The magnetic memory phenomenon on the friction surface was investigated under different sliding speeds and normal loads without lubricant. The result shown that there was a significant difference in the magnetic memory signal before and after wear. And the signal mutation of magnetic memory signal after wear appeared in the wear scar. The signal mutation indicated the location and the width of the wear scar accurately. By the signal gradient method,the peak area S,the distance of the intersection n and the gradient peak-to-peak V_pp in the wear scar could be known and they were different under the different condition and existed a particular relationship with the characteristics of the wear scar. Furthermore,by getting the eigenvalues of the gradient signal in the wear scar under the different dry friction condition,the phenomenon that the peak area S,the distance of the intersection n and the gradient peak-to-peak V_pp increased with the increasing of the sliding speed and the normal load were discovered.