Abstract: Objective To explore the relationships between the expression of PECAM-1 and the degree of ALI in Paraquat induced lung injury model of rabbits. Method Thirty six adult New Zealand rabbits were randomly divided into three groups: 8 mg/kg (Group A), 16 mg/kg (Group B) and 32 mg/kg ( Group C) according to the dose of Paraquat which were infusion into stomach. After poisoned, the animals were monitored for seven days, and then sacrificed. The upper lobe of lung were removed for HE,Masson staining and immunohistochemisty. The ALl score, fibrosis of lung and expression of PECAM-1 were semiquantitative analyzed. Results Each group has 12 animals suffered from poisoning. The survival time of animals in Group C was (6. 47 ± 0. 99 ) days, shorter than (6. 09 + 1.04) days ( P = 0. 031 ) in Group B and (4. 77 + 2. 04) days ( P = 0. 0 07) in Group A. The ALI score were ( 8. 33 ± 1.03) points in Group A, superior to (9. 83 ± 1.17) points ( P = 0. 047 ) in Group B and ( 11.50 + 1.38) points ( P < 0. 01 ) in group C, Group B vs Group C, P=-0.03o The fibrosis degree of lung was (31.09 +2.05)% in Group A,not severe as (34. 37 ±1.62)% (P=0. 002) in Group B and (36. 54 ±0. 44)% (P <0. 01 ) in Group C, Group B vs Group C, P = 0. 026. The Pearson correlation analysis showed the expression of PECAM-1 was negative correlated to ALI score (Coe = -0. 732, P =0. 001 ) and fibrosis degree of lung (Coe = -0. 779, P < 0. 001 ) . Conclusions The expressions of PECAM-1 were significantly decreased in New Zealand after Paraquat poisoned, which were dose dependent, correlated to ALI scored and fibrosis degree of lung, so it may play an important role in the development of lung injured induced by Paraquat.