error gui at debian9 (QXcbConnection: Could not connect to display)

I have compile the gui program by QT5.9 (sudo apt install qt5-default).
The compiling complete finely at lxqt and debian9:

sudo apt install qt5-default
cd program_directory
make clean

At lxqt, the binary program runs finely. But lxqt take up too much space, so I need in debian9.
But at debian9, running the binary file returns an error:
QXcbConnection: Could not connect to display

I have made:
export DISPLAY=:0.0
sudo apt install libffi-dev phantomjs gksu xserver-xorg

But the error is still present.

Also I can run the gui program at debian9 from another PC by:
ssh -X 192.168.X.X -l debian
but this doesn’t solve the problem.

I was advised here, and then my topic was deleted:
You are going to have to add enough stuff to provide, at minimum, an X
server implementation – and most likely you’ll need a window/desktop

The xserver is installed.

Please help.