Objective To investigate the expression levels of regulatory B cells (Bregs) in peripheral blood of patients with primary Sjgren’s syndrome (pSS) complicated with thrombocytopenia and analyze their clinical significance. Methods A total of 69 pSS patients treated at Mianyang Central Hospital from July 2021 to June 2022 were enrolled and divided into two groups: the pSS with thrombocytopenia group (n=33) and the pSS with normal platelet (PLT) group (n=36), based on the presence of immune-related thrombocytopenia. Additionally, 30 healthy individuals from the same period were included as a control group. Flow cytometry was employed to isolate lymphocytes based on surface CD markers, and the percentage levels of Breg subsets in venous blood were calculated, including CD19+CD24 hi CD38 hi B cells, CD19+CD5+CD1d+ B cells, and CD19+CD24+CD27+ B cells. Differences in Breg levels among the three groups were analyzed. Clinical data and laboratory parameters were compared between the pSS with thrombocytopenia and pSS with normal PLT groups, and logistic regression was used to identify risk factors for thrombocytopenia in pSS. Results Both the pSS with thrombocytopenia and pSS with normal PLT groups exhibited decreased percentages of CD19+CD24+CD27+ B cells compared to the healthy control group (P＜0.05), while the percentage of CD19+CD24 hi CD38 hi B cells was elevated in both pSS groups (P＜0.05). The pSS with normal PLT group showed a higher percentage of CD19+CD5+CD1d+ B cells than the healthy control group (P＜0.001), whereas the pSS with thrombocytopenia group had a lower percentage of CD19+CD5+CD1d+ B cells compared to the pSS with normal PLT group (P＜0.05). Hemoglobin (HGB) and complement C4 levels were significantly lower in the pSS with thrombocytopenia group than in the pSS with normal PLT group (P＜0.001 and P＜0.05, respectively). Logistic regression analysis revealed that a reduced percentage of CD19+CD5+CD1d+ B cells was an independent risk factor for thrombocytopenia in pSS (P＜0.05). Conclusion The percentage of CD19+CD5+CD1d+ B cells in venous blood significantly differs between pSS patients with thrombocytopenia and those with normal PLT levels. A decreased proportion of CD19+CD5+CD1d+ B cells is an independent risk factor for reduced platelet counts in pSS patients