Introduction and Objective: Endothelial progenitor cells (EPCs) have been proven to exhibit a therapeutic effect in deep vein thrombosis, but are susceptible to microenvironment. Besides, Matrine has promotive effects on EPCs, but its effects on microRNA (miR)-126 remain obscure, which are therefore discussed in the study. Methods: The cultured EPCs were extracted from Sprague-Dawley rats and identified by immunofluorescence assay. After being treated with Matrine or transfected with miR-126b inhibitor and small interfering RNA targeting forkhead box (FOXO) 4, the viability and apoptosis of EPCs were determined by cell counting kit-8 assay and flow cytometry. The migration, invasion, and tube formation abilities were detected by scratch, Transwell, and tube formation assays. The target genes of miR-126b were predicted by TargetScan, and verified by dual-luciferase reporter assay. The expressions of miR-126b, FOXO4, matrix metalloproteinase (MMP) 2, MMP9, and vascular endothelial growth factor (VEGF) A were determined by quantitative real-time polymerase chain reaction and Western blot. Results: The EPCs were successfully extracted and cultured, as evidenced by positive reaction cluster of differentiation (CD) 34 and CD133. Matrine promoted the viability, migration, invasion, and tube formation while inhibiting the apoptosis of EPCs, and upregulated the expression of miR-126b. Besides, miR-126b inhibitor reversed the effects of Matrine on EPCs and downregulated the expression levels of MMP2, MMP9, and VEGFA. MiR-126b targeted the FOXO4, and siFOXO4 reversed the abovementioned effects of miR-126b inhibitor on EPCs. Conclusion: Matrine protects EPCs from apoptosis and promotes their migration, invasion, and tube formation abilities via regulating miR-126b/FOXO4 axis. [ABSTRACT FROM AUTHOR]