After checking setup.py 8, I find that they use CUDA_HOME vairables. So i define CUDA_HOME Variable to point to the cuda7.5 folder  in my .bashrc file(Previously I define it to my PATH=/usr/local/cuda-7.5/bin:$PATH and LD_LIBRARY_PATH=/usr/local/cuda-7.5/lib64:$LD_LIBRARY_PATH ), I solved my problems.