I have solved this question after add "export QT_PLUGIN_PATH=/opt/Qt520/plugins/", now the Qt GUI demo could run at my 
QNX 6.6 vmware target successful. But from slog2info message, still have some error message:
(1)May 06 16:45:19.778                 qnxdemo.20495              default*  9000  QQNX: failed to open navigator pps, 
errno=2 
(2)May 06 16:45:19.782                 qnxdemo.20495              default   9000  QQnxVirtualKeyboard: Unable to open "/
pps/services/input/control" for keyboard: No such file or directory
(3)May 06 16:45:19.783                 qnxdemo.20495              default   9000  QQNX: failed to open buttons pps, 
errno=2

I don't know these error if effect my GUI demo normal working or performance, how to solve these error message.

This happens because your app cannot find some other parts of the Qt runtime, the qnx plugin. The qnx plugin implements 
integration with screen and other system services. Since the Qt runtime can be installed on various places in the file 
system on a target, there are a few environment variables which have to be set in the shell where the apps start to 
point to the location of the Qt runtime on the target. 

You might be interested to check this wiki page:

http://qt-project.org/wiki/QNX-App-development-and-deployment

PS. To explain to others and avoid confusions. In the course of preparation of the Qt 5.3 packages we are working on a 
new structure of the wikis. The target is to get Qt on QNX better documented on the well-known Qt sites, e.g. the wiki 
and the Qt docs themselves. We would focus this forum more in topics which are more QNX specific and less Qt generic.