The nano-sized polyaniline powders are synthesized in the ionic liquid/water micro-emulsion system.The ionic liquid/water (O/W) micro-emulsions which are composed of water and ionic liquid ［bmim］PF6 with aniline dissolved are prepared by use of emulsifier OP-10. It is the first time for ionic liquid to be used in micro-emulsion synthesis of polyaniline.The results of IR spectrometry and EDX show that ionic liquid doped polyaniline is synthesized successfully.The polyaniline exhibits good thermal and electrochemical stability and charge/discharge performance.