In order to investigate the relationship between proliferative activities and heat stress protein 70(HSP70) expression of porcine aortic endothelial cells(ECs) treated by benzo(a) pryene in vitro, porcine aortic endothelial cells were cultured in vitro, treated by different concentration of BaP(0, 0.5, 1, 10, 20 mumol/L) for 24 hours. Then, the proliferative activities and HSP70 expression of endothelial cells were determined by MTT and Western-blot respectively. The results showed that along with the rise of concentration of BaP, proliferative activities of porcine aortic endothelial cells decreased. There are not significantly difference of expression of HSP70 between and control and low-exposed cultures(0.5 mumol/L), but decreased at intermedieate and high concentration(1, 10, 20 mumol/L). It was suggested that BaP restrained proliferative activities of porcine aortic endothelial cells, which may be related to the inhibition of HSP70 expression by BaP.