试试下面的:
QLineEdit* pLineEdit = new QLineEdit(this) ;
pLineEdit->setFrameShape(QFrame::NoFrame) ;
QPalette palette;
QBrush brush(QColor(0, 0, 0, 0));
brush.setStyle(Qt::SolidPattern);
palette.setBrush(QPalette::All, QPalette::Base, brush);
pLineEdit->setPalette(palette);