In this report the features of the breakup of an auroral absorption substorm are discussed. In the longitudinal sector where the substorm breaks up, a sharp onset is preceded by weak absorption which intensifies as it moves equatorward. The maximum value of absorption after the onset depends on the intensification of the equatorward-moving absorption preceding the breakup. On the basis of the studied substorms it seems that before the onset the weak absorption decreases having a minimum just before the onset and that at longitudes near the breakup a sharp onset can be seen without any preceding absorption, or the minimum of the absorption preceding the onset lasts longer.