〔Abstract〕 Objective To explore the function of Slit2/Robo4/Rho signaling pathway in monocrotaline(MCT)-induced hepatic sinusoidal obstruction syndrome(HSOS). Methods Thirty-four rats were randomly divided into control group and experimental group. The rats in experimental group was established with MCT by gastric lavage(160 mg/kg), and randomly sacrificed after model making for 1 day, 2 days and 4 days. Serum alanine aminotransferase(ALT) and aspartate aminotransferase(AST) were measured by chemical method.Liver tissue damage was observed by HE staining and Masson staining. α-smooth muscle actin(α-SMA) protein expression in rat liver was measured by immunohistochemistry. The related indexes of Slit2/Robo4/Rho signaling pathway were measured by Western blot and RT-qPCR. Results After a single intragastric administration of MCT(160 mg/kg),the congestion of hepatic sinusoid, the degeneration of hepatocyte and central venous endothelial cell injury of the 1-day group were observed, the congestion and dilatation of hepatic sinusoid of the 2-day group was obvious, hepatic pathological changes were more serious of the 4-day group and perisinusoidal fibrosis was seen in the 4-day group. Compared with the control group, the liver index of the experimental group increased(P<0.05) serum AST of the 2-day group and the 4-day group increased(P<0.01), serum ALT of the 2-day group increased(P<0.01). α-SMA protein expression in rat liver of all treatment group was significantly higher than the control group(P<0.01). The expressions of Slit2, Robo4 mRNA and protein in each experimental group was lower than those of the control group(P<0.01) and gradually decreased with the prolonged administration time(P<0.05), while the expressions of RhoA,Rac1,Cdc42,matrix metalloproteinase(MMP)-2, MMP-9 mRNA and protein in each experimental group were higher than those of the control group(P<0.01) and gradually increased(P<0.05). Conclusion Rat HSOS was induced by single MCT, and rat liver injury was progressively aggravated. Slit2/Robo4/Rho signaling pathway, hepatic stellate cell activation and increase of MMP-2 and MMP-9 may be one of the important mechanisms of HSOS induced by MCT.