Objective To extract and identify primary culture rat pulmonary arterial smooth cells ( PASMCs) , and investigate the effects of hypoxia on the proliferation of PASMCs. Methods Rat PASMCs were separated by the method of tissue block anchorage, and the cellular morphology was observed under light microscope. The cells were identified by projection electron microscopy, and α-smooth muscle actin ( α-SMactin)in the cells was identified by immunohistochemistry and immunofluorescence. The primary cultured PASMCs were exposed to normoxic and/ or hypoxia condition for 2, 6, 12, 24, 48 hours respectively, thenMTT assay and PCNA ( proliferating cell nuclear antigen) immunohistochemistry were used to detect the proliferation of PASMCs. Results The cells tended to be long spindle and grew in the “peak-valley”mode under light microscope. Immunology results showed that endochylema was stained in brownish yellow, and the positive rate was beyond 96% . There were dense patch, dense body and many filaments in endochylema under projection electron microscopy. MTT assay demonstrated that the A values of PASMCs expose to hypoxia were higher than that of nomoxia. Comparing with normoxia, the A values of PASMCs exposed to hypoxia increased after 12 hours ( P lt;0. 05) , significantly increased after 24 hours ( P lt;0. 01) . Compared with 2 hours’exposure to hypoxia, the A values increased after 12 hours( P lt; 0. 05) , markedly increased after 24 hours ( P lt; 0. 01 ) , which after 48 hours was similar with 24 hours. The result of PCNA immunohistochemistry was consistent with that of MTT. Conclusions The tissue explants adherent method is simple and convenient, and can easily obtain rat PASMCs with high purity and stability. Hypoxia canpromote the proliferation of PASMCs.