To evaluate the efficacy of Compound Qinlan Oral Liquid in preventing and treating parainfluenza virus infection based on histopathology and the immune factors in serum and lung tissue homogenate.Methods:ICR mouse model was established by infection with parainfluenza virus(Sendai strain).Compound Qinlan Oral Liquid was administrated in high [22 mL/(kg·d)]，medium [11 mL/(kg·d)]，and low [55 mL/(kg·d)] doses，respectively.The therapeutic effect of Compound Qinlan Oral Liquid on the model mice was evaluated based on the pathological changes of lung tissue，as well as the levels of immune factors in the serum and lung tissue.Results:The high dose group reduced the lung index of model mice(P<005).The high，medium，and low dose groups decreased the lung index by 4947%，2968%，and 1846%，respectively，which showed a dose-dependent manner.The high and medium doses alleviated the bronchial lesions in model mice(P<005).The high dose group reduced the levels of inducible protein-10(IP-10)，monocyte chemoattractant protein(MCP)-3，macrophage inflammatory ptotein(MIP)-1α，RANTES，and Eotaxin(P<005)，and the medium dose group lowered that of MCP-3(P<005) in the serum.The high dose group reduced growth-related oncogene(GRO)-α，MCP-1，MCP-3，MIP-2，IP-10，MIP-1α，MIP-1β，and RANTES(P<005); the medium dose group reduced GRO-α，MCP-1，MCP-3，and MIP-2(P<005); and the low dose group reduced GRO-α(P<005) in the lung tissue.Conclusion:Compound Qinlan Oral Liquid has therapeutic effect on the pneumonia caused by parainfluenza virus infection，which can alleviate pulmonary bronchial lesions and reduce the immune factors in the serum and lung tissue.