Objective To improve the in-situ interfacial polymerization method for preparation of polypyrrole/ cotton (PPy/ Ctn) composite conductive materials. Methods The improved method with one step process in three phases was compared and analyzed with the traditional method with two steps in two phases. The effects of preparation conditions such as pyrrole concentration, dosage of the oxidizing agent, water bath ratio and oil bath ratio on the conductive property of the formed materials were discussed. The surface morphology of PPy / Ctn was characterized and a preliminary discussion on the main process through the interfacial polymerization process was also presented. Results An evenly distributed conductive polypyrrole layer with three-dimensional porous net- work structure and morphology was obtained on the cotton fabrics under the following conditions: pyrrole concentration was 0. 2 mol / L, dosage ratio of the oxidizing agent and the monomer was 1. 5, water bath ratio was 10 mL / g, oil bath ratio was 30 mL / g, TW-80 concentration was 2 g / L, reaction temperature was 0 ℃ and reaction time was 2 h. The polymerization reaction model was preliminarily established: pyrrole monomers were wrapped by surfactant micelle in the organic phase, approached to the surface of the cotton fabrics immersed in the aqueous phase, and then started in-situ polymerization under the initiation of Fe3+ adsorbed in fibers. Conclusion The adopted method of in-situ polymerization in water / fiber / oil three-phase system had the advantages of shorter time requirement, simple operation, material saving and suitable for larger area preparation. A flexible conductive composite with a surface resistance of 100 ~ 200 Ω / sq was obtained.