ObjectiveTo investigate the value of baseline red cell distribution width （RDW） and alkaline phosphatase （ALP） level after ursodeoxycholic acid （UDCA） treatment for one month in predicting the response to UDCA treatment in patients with primary biliary cholangitis （PBC）. MethodsA retrospective analysis was performed for the data of 127 patients with PBC who were diagnosed in Department of Hepatology， The Third People’s Hospital of Jiangsu University， from January 2015 to July 2022， with data collected at baseline， after one month of treatment， and after one year of follow-up. Based on the Paris-I criteria， the patients were divided into good response group and poor response group， and the two groups were analyzed in terms of clinical and laboratory features and their association with response to UDCA. The Logistic regression method was used to investigate the independent risk factors for response to UDCA treatment. The area under the ROC curve （AUC） was used to determine the optimal cut-off values of related indicators； the patients were divided into two groups based on such values， and the two groups were compared in terms of baseline indicators and response. The independent-samples t test was used for comparison of normally distributed continuous data between two groups， and the Mann-Whitney U test was used for comparison of non-normally distributed continuous data between two groups； the chi-square test was used for comparison of categorical data between two groups. ResultsCompared with the good response group， the poor response group had significantly higher levels of total bilirubin， aspartate aminotransferase/alanine aminotransferase， ALP， RDW， and RDW-CV at baseline and a significantly higher level of ALP after one month of UDCA treatment （Z=-4.792， -3.697， -2.399， -4.102， -3.220， and -4.236， all P<0.05）. Compared with the good response group， the poor response group had significantly lower levels of albumin， hemoglobin， lymphocytes， hematocrit， and body mass index at baseline （Z=-3.592， -3.603， -2.602， -3.829， -2.432， all P<0.05）， as well as significantly lower levels of prealbumin， albumin/globulin ratio， apolipoprotein A， and free triiodothyronine at baseline （t=4.530， 3.402， 3.485， and 3.639， all P<0.001）. Compared with the poor response group， the good response group had a significantly lower proportion of patients with liver cirrhosis， gallstones/cholecystitis， or anemia （χ²=20.815， 3.892， and 12.283， all P<0.05）. Baseline RDW （odds ratio ［OR］=1.157， 95% confidence interval ［CI］： 1.028‍ — ‍1.301， P=0.015） and ALP level after one month of treatment （OR=1.012， 95%CI： 1.005‍ — ‍1.020， P=0.002） were independent risk factors for response to UDCA， with an AUC of 0.713 and 0.720， respectively. The patients with baseline RDW≥upper limit of normal （ULN） and ALP≥2.2×ULN after one month of UDCA treatment had a lower UDCA response rate （42.6% vs 8.2%， χ²=20.813， P<0.001）. ConclusionPatients with baseline RDW≥ULN and ALP≥2.2×ULN after one month of UDCA treatment tend to have a low biochemical response rate to UDCA.