Seems you need to enable mouse tracking for widget1, see:

void setMouseTracking(bool enable)
If mouse tracking is switched off, mouse move events only occur if a mouse button is pressed while the mouse is being moved. If mouse tracking is switched on, mouse move events occur even if no mouse button is pressed.

I solved my problem via event filter of scene.

ui->graphicsView->scene()->installEventFilter(this); bool MainWindow::eventFilter(QObject* obj, QEvent* event){ if(event->type() == QEvent::GraphicsSceneMousePress){ if(ui->addServerBtn->isChecked()){ QGraphicsSceneMouseEvent* mouseSceneEvent; mouseSceneEvent = static_cast<QGraphicsSceneMouseEvent *>(event); Server *serv = new Server(mouseSceneEvent->scenePos().toPoint()); scene->addItem((QGraphicsPixmapItem*)serv); } } return false; }