Abstract: Based on grey relational analysis, the relation changes between the environmental factors and corrosion rate of 2Cr13 and 1Crl8Ni9Ti were examined. It was shown that the changes of influencing factors of 2Cr13 and 1Crl8Ni9Ti varied due to exposure time. The atmosphere corrosion rate of 2Cr13 was affected mainly by the time when the relative humidity was greater than 80% in a year, rainfall, temperature and Cl^- in the initial stage, while later affected by Cl^-, SO₂, the time when the relative humidity was greater than 80% in a year, relative humidity, and temperature. The relation sequence between the environmental factors and corrosion rate of 2Cr13 was changing ceaselessly in different periods of time. The corrosion rate of 1Crl8NigTi was affected by the time when the relative humidity was greater than 80% in a year, rainfall, dust and so on in initial stage. The effect of Cl^- was boosted up with corrosion time. Cl^- became the leading factor of 1Crl8Ni9Ti gradually. The relation sequence stabilized between the environmental factors and corrosion rate of 1Crl8Ni9Ti after long-term exposure.