QTableWidget with many cellwidgets update very slow!

[wysota]

I want to implement customized drag and drop for item in qtablewidget, so I use qlabel as cellwidget.
If no use cellwidget, then what to use?

You don't need cell widgets to have custom drag and drop. QTableWidget already offers required facilities. Even more is offered if you use a proper model-view approach (i.e. QTableView nad QAbstractTableModel subclass instead of QTableWidget).