A new carbon nanotube (CNTs)–poly acrylonitrile (PAN) composite electrolyte was prepared by the thermal polymerization of acrylonitrile (AN) with CNTs for solid-state dye sensitized solar cells (DSSCs). It was found that the uniform CNT–PAN composite was formed due to the thermal polymerization of AN on CNTs. The strong bonding between CNTs and PAN could be confirmed by the characterization of XPS and Raman spectroscopy, resulting in the lowering of crystallinity and the increasing the ionic conductivity of composite electrolytes. On comparison with bare CNTs and the other composite electrolytes, the formation of triiodide (I3 −) ions in CNT–PAN composite electrolytes was drastically increased which was expected from the high ionic conductivity of electrolyte via I3 −/I− redox couple. DSSCs fabricated with CNT–PAN composite electrolytes achieved relatively high conversion efficiency of 3.9% with an open circuit voltage (V OC ) of 0.57V, short circuit current density (J SC ) of 10.9mA/cm2 and fill factor of 63.6%, which attributed to supply the higher extent of I3 − ions from CNT–PAN composite electrolyte during the charge transport process.