#include <QTextCodec>
{
...
QFont font("wenquanyi", 160);
setFont(font);
QTextCodec::setCodecForLocale(QTextCodec::codecForName("UTF-8"));
QTextCodec::setCodecForCStrings(QTextCodec::codecForName("UTF-8"));
QTextCodec::setCodecForTr(QTextCodec::codecForName("UTF-8"));
...
}