Thanks for help. I apply this function to MainWindow and it works well:

Qt Code: 
  1. void translateFontSize( QWidget *ui )
  2. {
  3.     QObjectList l;
  4.     QObject *w;
  5.  
  6.     if (!ui)
  7.         return;
  8.  
  9.     QFont font = QFont(ui->font());
  10.     font.setPointSize( (font.pointSize() *4) / 3);
  11.     ui->setFont(font);
  12.  
  13.     l = ui->children();
  14.  
  15.     foreach (w, l) {
  16.         QWidget *ww = dynamic_cast<QWidget *>(w);
  17.         if (ww) {
  18.             translateFonts( ww );
  19.         }
  20.     }
  21. }
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