Objective To investigate the effects of sodium tanshinone ⅡA sulfonate(STS) on serum level about tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and leukotriene B4 (LTB4) and 5-lipoxygenase protein and mRNA expression in paraquat poisoning rats lung. Methods Sprague - Dawley (SD) male rats were randomly divided into control group, paraquat group, STS group. Each group was made up of 25 rats. Rats in control group were injected by 2 mL intraperitoneal injection of saline. Rats in paraquat group were given saline diluting paraquat 50 mg/kg to 2 mL lavage infected. Rats in STS group were given 25 mg/kg STS by intraperitoneal injection after paraquat poisoning, and were injected continuously for three days. After the model was completed 72 h groups rats were executed respectively. The heart was taken, and the abdominal aorta blood was collected for PO₂ inspection. The lung tissue specimens were stained by turbulence eosin (HE) staining, and then were observed the lung tissue pathology. The serum concentration of TNF-α, IL-6 and LTB4 was detected by enzyme-linked immunoassay. 5-LOX protein expression was detected by Western blotting testing. 5-LOX mRNA expression was detected by real-time fluorescent quantitative PCR. Results ①It can be seen that lung tissue structure is clear, pulmonary interstitial and alveolar was normal in the control group. In paraquat group, a large number of inflammatory cells infiltrated in the rat lungs, and pulmonary became edema and pulmonary interstitial fractured. In STS group, rat pulmonary interstitial and alveolar congestion edema relieved obviously, a small amount of inflammatory cell infiltrated. ②Rat arterial blood gas PO₂ was significantly lower in paraquat and STS groups than that in control group (P<0.01). In STS group, arterial blood gas PO₂  was significantly higher than that in paraquat group (P<0.01). ③In paraquat and STS group, serum concentration of TNF-α, IL-6 and LTB4 was significantly higher than that in control group (P<0.01). In STS group, serum concentration of TNF-α, IL-6 and LTB4 was significantly lower than that in paraquat group (P<0.01). ④In paraquat group, the amount of 5-LOX protein expression in rat lung tissue was significantly higher than that in control group and the STS group (P<0.01). In STS group, 5-LOX protein expression in rat lung tissue was lower than that in control group (P<0.05). ⑤In paraquat and STS group, 5-LOX mRNA expression in rat lung tissue was significantly higher than that in control group (P<0.01). In STS group, 5-LOX mRNA expression in rat lung tissue was significantly lower than that in paraquat group (P<0.01). Conclusion STS may restrain 5-LOX expression to inhibit LTB4 releasing, reducing inflammation cascade reaction. STS may suppress lung injury in rats of paraquat poisoning.