Polyacrylonitrile(PAN)-lithium bis(trifluoromethane sulfone)imide (LiTFSI) complex has been investigated by X-ray diffraction (XRD) and vibrational spectroscopy Two kinds of amorphous complexes are found in the salt-in-polymer and polymer-in-salt regime, respectively. Phase transition is observed by XRD as the content of lithium salt increases from P(AN)(6)-LiTFSI to P(AN)(2)-LiTFSI. It is also evidenced by Fourier Transform infrared (FTIR) and Raman spectroscopic studies. Interactions between the Li ion and host polymer are clarified by comparing the spectral evolution of the -C=N group before and after LiTFSI was complexed with PAN. However, the LiTFSI addition has no obvious influence on the -CH2 group of PAN, evidently different from that observed with PEO. Li+ ions coordinate also with O and/or N of anions, probed by the spectral changes of -SNS and -SO2 groups.