Previous studies have suggested that systemic sclerosis-associated interstitial lung disease (SSc-ILD) progresses rapidly in the early stage of the disease course, but the disease course stabilizes or even stops progressing 4 years after diagnosis. This study aims to determine whether there are different prognostic phenotypes of SSc-ILD by observing whether there is a significant plateau in the course of pulmonary function decline in SSc-ILD patients and whether there is a correlation between different prognostic types. Methods: This study cohort came from an SSc-ILD specialized clinic, and included SSc-ILD cases admitted from January 1998 to June 2016. The diagnostic criteria of SSc were referred to the diagnostic criteria of ACR, while ILD was determined by thoracic HRCT; Follow-up was performed every 6 months (pulmonary function, 6-min walk test, and annual color ultrasound). According to the survival period, they were divided into three groups: long-term survival group (survival>8 years), intermediate death group (survival 4 to 8 years) and short-term death group (survival<4 years). Follow-up period excluded<Patients of 8 years. The generalized linear model was used to calculate the FVC for each patient as % of the predicted value and DLThe slope of the decrease in CO as % of the predicted value to compare the rate of decrease in FVC as % of the predicted value between different prognostic groups. Results: (1) A total of 171 patients with SSc-ILD were screened. The median survival time was 11.2 years, including 37 patients in the long-term survival group, 19 patients in the middle-term death group and 25 patients in the short-term death group. The remaining 90 patients who had been followed up for less than 8 years at the end of the study were excluded. (2) Throughout the entire cohort (FIG. 1A), FVC accounted for an average of 1.06% per year in % of the predicted value, showing a significant decrease in the first 4 years of the disease course, a significant plateau period between 4 and 8 years of the disease course, and a significant decrease after 8 years of the disease course. (3) Baseline FVC accounted for 80% of the projected value in the long-term survival group and 70% in the other two groups. The decreasing curves of FVC as % of the predicted value of the three groups all showed a nearly linear decreasing trend, and there was no obvious plateau period (Figure B). Annual FVC in the short-term death group as % of the projected value and DLThe decrease rate of CO as % of the predicted value was greater than that of the other two groups (P =0.006 andP<0.001)。 (4) Through statistical analysis, it is found that the change trend of FVC in the previous year in % of the predicted value cannot predict the change of FVC in the next year. However, the previous year DLThe change trend of CO as % of the projected value can predict the next year's DLChanges in CO as % of the projected value, i.e. the previous yeardLCO % of the projected value If the trend is stable or declining, the D of the next yearLCO accounted for % of the projected value also showed a flat or downward trend. Conclusion: Adult patients with SSc-ILD have different types of pulmonary function progression, and their progression trends show consistent before and after during long-term follow-up. However, in the short term, the recent trend of changes in FVC as % of the predicted value cannot predict the future changes in FVC as % of the predicted value in such patients. Clarifying the characteristics of pulmonary function decline in patients with SSc-ILD can help improve clinical decision-making for such patients and guide the design of rational clinical trials.