Abstract: A novel method based on in-situ polymerization was used to prepare PTT/wool/PANI composed conductive yarns continuously. The effect of concentration of reaction liquid on the electrical conductivity of composite yarns was discussed, and the surface morphology, chemical construction and mechanical property of composite yarns were also studied. The results indicated that, the electrical conductivity increased with the concentration of reaction liquid, and the electrical conductivity of composite yarn can reach to 1.08×10-2S/cm. the FITR curves indicated that the composite yarn was a blending system of PTT fiber, wool fiber and PANI. The yarn’s breaking strength, breaking elongation and initial modulus increased after conductive processing, while the yield strength and elongation decreased.