Abstract： Objective To study the significance of leukocyte and neutrophil in paraquat poisoning.Methods Totally 139 cases of paraquat poisoning were divided into four groups according to the degree of lung injury:none pulmonary injury group (35 cases),mild pulmonary injury group (26 cases ),moderate pulmonary injury group(18 cases)and severe lung injury group(60 cases);meanwhile they were divided into three groups according to the results of treatment:cure group(86 cases),death within 3 days group(22 cases),the death after 3 days group(31 cases).60 cases of severe lung injury were divided into 3 groups:severe lung injury cure group (8 cases),severe lung injury death within 3 days group(22 cases),the severe lung injury death after 3 days group (30 cases).The relation between peripheral blood leukocyte and neutrophil number with lung injury was observed.Results Leukocyte and neutrophil number in severe lung injury patients were significantly increased [ (9.2±3.0)× 109/L,(9.6±3.6)× 109/L,(10.3±4.7)× 109/L vs (18.6±7.6)× 109/L;(7.1±2.8)× 109/L,(7.5±3.7)× 109/L,(8.0±3.8)× 109/L vs (16.1±6.9)× 109/L,all P＜0.05 ].Leukocyte and neutrophil count in the 2 groups of death were significantly higher than those of the cure group.Leukocyte and neutrophil count of the patients in severe lung injury cure group started to decline and showed significant difference from in two severe lung injury death groups since third day [ (22.0±7.2 )× 109/L vs (16.4±6.5 )× 109/L vs (9.5±4.7)× 109/L;(19.0±6.4)× 109/L vs (14.2±5.6)× 109/L vs (7.8±4.5)× 109/L,all P ＜0.05].Conclusions The more severe lung injury is,the lager number of leukocyte and neutrophils there is. If the patient's white blood cell and neutrophil count decrease rapidly to normal within 3-5 days and remain within the normal range after discontinuation,there is usually a good prognosis.