bool bIsExist = false; // 进程是否存在
QProcess process;
process.start("tasklist.exe");
if (process.waitForFinished())
{
    QByteArray result = process.readAll();
    QString exe = QString(result);
    if (exe.contains(strProcessName))
    {
        bIsExist = true; // 找到了
    }
}
process.close();

//结束进程
QStringList list;
list << "/im" << strProcessName << "/f";
QProcess::execute(QLatin1String("taskkill"), list);