CompositesSulfonated Polyphenylacetylene/Multiwalled Carbon Nanotube（SPPA/MWNT）were prepared by mixing SPPA with MWNT under ultrasonic bath. The composites were studied using Fourprobe, X-Ray photoelectron Spectroscope, UV-Vis-NIR spectrophotometer, X-Ray diffraction, Field Emission Scanning Electron Microscope (FESEM) ,etc. The results show strong interactions between MWNT and SPPA as well as a behavior of Negative Temperature Coefficient (NTC) of resistance. The phenomenon of the low percolation threshold and twice obvious increases of electrical conductivity were also found in the composites. It is assumed that SPPA with higher electrical conductivity due to charge transfer between SPPA and MWNT，which were affected by interaction, contacts with each other. Thus it forms conductive networks in the composites.