It is generally thought that the quality management and the six-sigma management innovation are not applicable to service industry, which might be derived from some differences between service and manufacturing industries. However, both are substantially alike in some intrinsic attributes. KT is leading the quality management and the six-sigma innovation activities in service industry, especially among telecommunication companies in Korea. Six sigma management innovation has been fostered in KT within short period of time and played an important role in helping KT privatized successfully. The successful cases of six sigma innovation activities in KT could be introduced to other Korean companies in service industry. Five key factors for the success of six-sigma innovation activities are suggested, The hidden factory in all the fields of company should be eliminated. Six-sigma projects need to be connected with the company strategy. The project should be carried out intensively in a short time. The innovation activities in the field need to be integrated. The best practice of six-sigma should be disseminated in the field.