Abstract： Objective:To examine the expression of core clock genes in the peripheral blood mononuclear cells (PBMCs) and the level of circadian disturbance-related proteins in the serum of chronic pancreatitis (CP) patients with pancreatic exocrine insufficiency (PEI), and explore their potential diagnostic value in clinical practice.Methods:The peripheral blood samples and related clinical data from 68 patients diagnosed with CP in Shanghai General Hospital from Jan 2015 to Jan 2022 were collected. Peripheral blood samples from 30 healthy individuals were used for control. The M-ANNHEIM classification system was used to stratify the clinical stages of patients with CP. The mRNA expression of the core clock genes, including Clock, Bmal1, Per1/2/3 and Cry1/2 in PBMCs was analyzed using realtime qPCR, and the expression of circadian disturbance-related proteins like TrkB, CD 36 and Rbp in serum was measured with ELISA. The receiver operating characteristic curve(ROC) and the area under curve (AUC) was used to test the efficiency for diagnozing PEI. Results:The mRNA expression of Per1 in CP patients was significantly decreased (0.76 vs 1, P<0.05), and the AUC for diagnozing PEI was 0.744 (95% CI 0.628-0.860), with a cut-off value of 0.72; and the sensitivity and specificity was 84.8% and 57.1%, respectively. The protein abundance of serum CD 36 was significantly increased in CP patients (33.85±19.74ng/ml vs 24.71±11.53 ng/ml, P<0.05); the AUC for diagnozing PEI was 0.834 (95% CI 0.735-0.932), with a cut-off value of 29.75 pg/ml; and the sensitivity and specificity was 74.3% and 84.8%, respectively. The expression of CD 36 was increased with the increase of CP clinical stage, and there were statistically significant differences between either two stages (all P value <0.05). The mRNA expression of Per1 in patients with CP in Stage Ⅰ was significantly higher than that in patients with CP in Stage Ⅱ or Ⅲ, and the differences were statistically significant ( P<0.05), but no statistical difference was found between Stage Ⅱ and Stage Ⅲ. Conclusions:The decreased expression of Per1 mRNA in PBMCs and increased level of CD 36 in serum are significantly related to the occurrence of PEI in CP, suggesting that they may have potential value for diagnozing PEI and guiding the clinical practice.