Abstract: Objective: To assess whether there is a correlation between CT scan severity score and pulmonary function in Interstitial Lung Disease, and provide a more reliable basis for clinical diagnosis and treatment. Materials and Methods: Sixty patients with clinical diagnosis of Interstitial Lung Disease (ILD) were collected, and chest CT and pulmonary function tests were performed at the same time. Here DLCO% and FEV1% were used as the pulmonary function indexes. The severity of the patients was assessed by CT scores as mild (range, 1~10), moderate (range 11~20), and severe (range 21~30). Correlation analysis was carried out between CT score and pulmonary function index, and the lung function parameters of patients at three grades were compared between groups and pairwise among the means. Results: As per the CT severity classification, there were 13 mild cases, 31 moderate cases, and 16 severe cases. CT score was negatively correlated with DLCO% and FEV1%. R value was −0.814 and −0.797, respectively; The comparison of the mean value of DLCO% and FEV1% among the three groups and the pairings of the mean value of DLCO% and FEV1% were statistically significant. Conclusion: There was good correlation between CT score of ILD and the pulmonary function index. The pulmonary function index of patients with different CT severity grading was statistically significant, which can provide a new basis for the clinical evaluation and diagnosis of the disease.