The effect of ionic group content and main chain structure of copolyesters on the electrical conductivity of polypyrrole/copolyester composite films was investigated. The composite films were prepared by polymerizing pyrrole through vapor phase absorption onto the copolyester films that contained FeCl3. The conductivity of polypyrrole/copolyester composite films increased with the DMS content and reached its maximum when the DMS content reached about 10 mol%. The conductivity increased dramatically when DMS content was more than 5 mol% that was considered as the critical composition for polypyrrole continuity. The conductivity increased with the EG content at the same DMT/DMI ratio and showed maximum when DMT:DMI ratio was 1:1.