Abstract: Adopting the Six Sigma process and using related methods like logistic regression，chi-square test and process certification，etc.，the key factors effecting qualification rate of the eddy current testing to high pressure boiler tubes are identified，including piercing plug service life，phosphating flush，acid solution temperature and concentration，and bathing time，and rolling mill signal and dust purging etc.Accordingly，modification plan is determined.Thanks to implementation of the Six Sigma management process，the said qualification rate has enhanced from the original 93.21%to 95.71%，while the Six Sigma level is lifted from the original-1.44 to 0.66，resulting in enhancement of both operation cost-effectiveness and economic profit of the company as well.