Objective To investigate the risk factors, clinical characteristics and prognostic factors of venous thrombosis (and pulmonary embolism) in patients with idiopathic hypereosinophilia (IHE) so as to provide a theoretical basis for clinical prevention of venous thrombosis and improve prognosis.Methods Thirty-nine patients with IHE admitted to West China Hospital of Sichuan University from January 2010 to January 2022 were collected in this retrospective case-control study to explore the risk factors of venous thrombosis (including pulmonary embolism) and thrombosis recurrence after treatment. Results There were 17 (43.5%) patients combined with venous thrombosis of 39 patients with IHE. In the patients with vascular involvement, pulmonary embolism was the initial expression of IHE accounted for 29% (5/17). patients of IHE with pulmonary embolism were younger [44 (24.5 - 51.0) vs. 56 (46.3 - 67.8) year, P=0.035] and had higher peak absolute eosinophil counts [11.7 (7.2 - 26.5)×109/L vs. 3.8 (2.9 - 6.7)×109/L, P=0.020] than those without pulmonary embolism. After a mean follow-up of 13 months (2 - 21 months), thrombosis recurred in 35.3% (6/17) of patients. Persistent increasing in eosinophils (>0.5×109/L) was an independent risk factor for thrombus recurrence (odds ratio 13.33, 95% confidential interval 1.069 - 166.374). Conclusions Thrombosis is a common vascular impaired complication in IHE , and increased eosinophilia is a risk factor for thrombosis and thrombus recurrence after therapy. Controlling and monitoring the eosinophilic cell levels in patients with IHE may avoid severe comorbidities.