QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL");
db.setHostName("192.168.100.138");
db.setPort(53);
db.setDatabaseName("SCM");
db.setUserName("SCM");
db.setPassword("SCM");
if (!db.open())
qWarning() << "Failed to connect to root mysql admin";
输出

------解决方案--------------------
make clean一下再执行qmake&make试试看。PATH变量一定要对!
曾经遇到过类似的情况。