Abstract: Objective To study the changes of cytoskeleton during the phenotypic transition of rat pulmonary artery smooth muscle cells (PASMCs) induced by platelet-derived growth factor (PDGF-BB), and to explore the mechanism involved in the process of phenotypic transition of PASMCs. Methods PASMCs of Sprague Dawley (SD) rats were cultured and identified by immunohistochemistry (IHC) method. The cells were randomly divided into control group and PDGF-BB treated group (10 ng/mL). RT-qPCR and Western blot were used to detect the mRNA and protein level of marker genes (α-SMA and SM22α) during the process of phenotypic transition of PASMCs. The changes of cytoskeleton were observed by fluorescent microscopy, cell proliferation was measured by CCK-8 method; and cell migration was observed by wound healing assay. Results Compared with control group, PDGF-BB down-regulated the mRNA and protein expression of α-SMA and SM22α. The fluorescence intensity of cytoskeletal protein was significantly reduced after the treatment of PDGF-BB. In addition, the structure of F-actin was disorganized with a burr-like appearance, and the structures of α-tubulin and β-tubulin were irregular with co-location appearance. PDGF-BB significantly enhanced the proliferation and migration of PASMCs. Conclusion PDGF-BB could induce a conformation change in cytoskeletal proteins for PASMCs phenotypic transition, and enhance the ability of proliferation and migration of PASMCs.