I found that most of those plugins in my static qt directory has .a files
but /plugins/phonon_backend is an exception
there is only a libphonon_gstreamer.so in it,no .a file!

and then I configured and made again with argument -static -phonon-backend
but it didn't change anything

then I look into the shared qt dirctory installed by the .bin file I downloaded from qt's website.
Look in /qt/plugins/phonon_backend ,there is also no .a file while all the other folders in that directory has both .a and .so files of the same name

So I am totally confused now
I have found that static compile can solve my original problem
!!!but the problem now I think is that
I statically compile qt,but I can't get a static phonon_backend lib

what's wrong with my Qt?will a totally reinstall and remake for static solve this problem?
plz help me.
best wishes to everyone.
I hate confusion really.