Thank you for reply.
`make clean` in "src/cudamatrix" and `make`.
Then `make ext` in "src/" for online extensions installation.
But the error still occurred.
I found that I can type the command "nnet-forward" directly and it returns usage manual.
linux-vdso.so.1 => (0x00007ffd1268f000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fa562aaf000)
libkaldi-nnet.so => /usr/local/kaldi-trunk_test/src/lib/libkaldi-nnet.so (0x00007fa562809000)
libkaldi-cudamatrix.so => /usr/local/kaldi-trunk_test/src/lib/libkaldi-cudamatrix.so (0x00007fa5622b7000)
libkaldi-lat.so => /usr/local/kaldi-trunk_test/src/lib/libkaldi-lat.so (0x00007fa561af8000)
libkaldi-hmm.so => /usr/local/kaldi-trunk_test/src/lib/libkaldi-hmm.so (0x00007fa5615d7000)
libkaldi-tree.so => /usr/local/kaldi-trunk_test/src/lib/libkaldi-tree.so (0x00007fa5612ae000)
libkaldi-matrix.so => /usr/local/kaldi-trunk_test/src/lib/libkaldi-matrix.so (0x00007fa560f84000)
libkaldi-util.so => /usr/local/kaldi-trunk_test/src/lib/libkaldi-util.so (0x00007fa560d12000)
libkaldi-base.so => /usr/local/kaldi-trunk_test/src/lib/libkaldi-base.so (0x00007fa560b09000)
libfst.so.1 => /usr/local/kaldi-trunk_test/tools/openfst/lib/libfst.so.1 (0x00007fa56066a000)
/usr/local/kaldi-trunk_new/tools/ATLAS/build/install/lib/libsatlas.so (0x00007fa55fd67000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fa55fa61000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fa55f843000)
libcublas.so.7.5 => /usr/local/cuda/lib64/libcublas.so.7.5 (0x00007fa55df64000)
libcudart.so.7.5 => /usr/local/cuda/lib64/libcudart.so.7.5 (0x00007fa55dd06000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fa55d9f9000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fa55d7e2000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fa55d41d000)
/lib64/ld-linux-x86-64.so.2 (0x00007fa562cb3000)
libgfortran.so.3 => /usr/lib/x86_64-linux-gnu/libgfortran.so.3 (0x00007fa55d0fc000)
librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fa55cef4000)
libquadmath.so.0 => /usr/lib/x86_64-linux-gnu/libquadmath.so.0 (0x00007fa55ccb5000)
So I don't know why it still loaded the 6.5 one.