QString str = QString("%L1").arg(yourDouble);

据说可以，但是怎么用还没搞懂

const QLocale & cLocale = QLocale::c();
QString ss = cLocale.toString(yourDoubleNumber, 'f');
ss.replace(cLocale.groupSeparator(), yourGroupChar);
ss.replace(cLocale.decimalPoint(), yourDecimalPointChar);