Abstract: Objective　To analyze the relationship between inflammatory indexes and thrombotic events in patients with primary thrombocytosis (ET) and polycythemia vera (PV), so as to provide basis for the judgment and treatment of thrombosis. Methods　The clinical data of 97 patients with bone marrow proliferative tumor (MPN) including 54 cases of ET and 43 cases of PV were analyzed retrospectively. According to whether there were thrombotic events, the patients were divided into the thrombotic group (n=52) and the non-thrombotic group (n=45). The receiver operating characteristic (ROC) curve was drawn to evaluate the predictive value of neutrophil lymphocyte ratio (NLR), high-sensitivity C-reactive protein (hs-CRP) and positive pentameric protein 3 (PTX3) in thrombosis. The clinical characteristics of patients were compared between the thrombotic group and the non-thrombotic group. Multivariate Logistic regression analysis was used to analyze the risk factors of thrombotic events. Results　Among 52 patients with thrombotic events (53.61%), 28 patients (51.85%) were in the ET group and 24 patients (55.81%) were in the PV group. The results of ROC curve showed that the best cut-off values of NLR, hs CRP and PTX3 were 3.14, 1.75 mg/L and 0.915 μg/L, respectively. The incidence rates of thrombotic events were higher in the high-level NLR, hs-CRP and PTX3 groups than that in the low-level group (χ2 were 15.715, 15.255 and 18.657, respectively, P＜0.01). In all patients, the age, hs CRP, PTX3, NLR and JAK2 gene positive rates were significantly higher in the thrombotic group than those in the non-thrombotic group (P＜0.05). Multivariate Logistic analysis showed that the elderly and high PTX3 level were independent risk factors for thrombotic events in all patients, and the elderly were independent risk factors for thrombotic events in patients with ET or PV (P＜0.05). Conclusion　ET and PV patients with high levels of hs-CRP, PTX3 and NLR have a higher incidence of thrombotic events. Age and PTX3 levels can be used as important indicators to assess thrombosis in patients.