Reconfiguration methods and devices are disclosed for scan chains with the planned unit taken into consideration, the one method comprising a first phase reconfiguration and second phase reconfiguration. The first phase reconfiguration first classifies a number of scan chains, wherein scan chains with the starting point and the ending point in the same planned unit are classified as a first aggregation of scan chains; scan chains with the starting point and the ending point not in the same planned unit are classified as a second aggregation of scan chains; and scan chains with both the starting point and the ending point at the same top level are classified as a third aggregation of scan chains. In sequence the scan chains within the first aggregation are reconfigured, then the scan chains within the second aggregation are reconfigured, and finally the scan chains within the third aggregation are reconfigured.