I split 2 columns my contetnt node with Display Suite and add custom class to the columns. (with Bootsrap responsive class col-sm-3) But display suite still render column with old style: group-left and group right. How can i remove old style?
The classes are only added to the existing ones, they don't replace them. If you want to remove the old styling, you can create a new layout and either add different default classes, or no classes at all.
You also might want to consider using Display Suite Bootstrap Layouts. Bootstrap 3.0 layouts are still in dev, but it's worth taking a look.