A composite of polyaniline (PANI) encapsulating mutilwall carbon nanaotube(MWNT) composite nanotube with nanometer size has been synthesized by insitu emulsion polymerization. Nanotube dimensions have been measured and the nature of the association between the components have been observed using SEM and TEM techniques, the diammer of nanocomposite tube is about 6070 nm.The improvement of thermal stability and crystallinity of nanocomposites have been evaluated by using TGA and XRD. The photoconductivity of PANIMWNT composite nanotube has been enhanced markedly and discussed by taking the photoinduced charge transfer between PANI and MWNT into consideration.