Objective To investigate the effects of different fine particulate matter (PM2.5) components (water-soluble, organic, water-soluble+organic) in vivo on the NOS/NO system in the endothelial cells from rat thoracic aortas. Methods Three PM2.5 components were used to inject by vein in rat tail. ELISA and immunohistochemical technique were used to examine the change of NOS/NO system in the blood-serum and the endothelial cells from rat thoracic aorta. Results Compared with control group, three PM2.5 components increased NO level of rat blood-serum [control, (38.00±5.40) μmol/L; water-soluble group, (44.66±16.59) μmol/L, t =3.58, P< 0.05; organic groups, (58.28±12.30) μmol/L, t =12.85, P <0.01; mixtural component group, (84.02+19.24) μmol/L, t =31.39, P<0.01]; increased iNOS level of rat blood-serum [control, (17.47±5.33) U/ml; water-soluble group, (21.87±4.63) U/ml, t =4.92, P <0.05; organic groups, (25.27±6.58) U/ml, t = 6.22, P<0.05; Mixtural component group, (32.79±5.86) U/ml, t =32.84, P <0.01]. Mixtural component decreased eNOS level of rat blood-serum [(12.58±4.59) pg/ml vs (17.47±2.97) pg/ml, t =5.91, P <0.05], no significant difference on eNOS level of blood-serum among other component groups (P >0.05). Three components decreased the expression of eNOS protein in the endothelial cells from rat thoracic aorta(control, 164.68±4.80; water-soluble group, 185.43±5.63, t =4.26, P <0.05; organic groups, 194.07±9.77, t =5.26, P <0.05; Mixtural component group, 209.24±15.43, t =43.19, P <0.01), increased the expression of iNOS protein (control, 160.17±5.79; water-soluble group, 134.78±8.22, t =5.21, P <0.05; organic groups, 134.78±8.22, t =5.98, P <0.05; Mixtural component group, 81.62 ±10.59, t =34.98, P <0.01) in the endothelial cells from rat thoracic aortas.Conclusion Three components of PM2.5 induced the dysfunction of endothelial cells and disorder of NOS/NO system in the endothelial cells.