Objective To study the regulation effect of Yupingfeng San on the expression of ICAM in mice pharynx mucous membrane when flora imbalance causes upper respiratory tract infection. Methods 30 SPF Kunming mice were randomly divided into three groups：normal control group， model group and Yupingfeng San group. The model group by intraperitoneal injection of ampicillin induced flora imbalance model of the upper respiratory tract. Yupingfeng San group in building models were treated by gastric perfusion With Yupingfeng San. 7 days later， the pharyngeal mucosal tissues were fixed and ICAM was measured by immunohistochemical staining in these tissues. To observe the positive expression under the microscope and calculate the average optical density of the positive results using image analyzer. Results In the model group， the expression of ICAM increased than the control group（P<0.01）， while the expression of ICAM in Yupingfeng San group than those in the model group decreased significantly （P<0.01）. Conclusion Pharyngeal infection by flora imbalance can promote the expression of ICAM in mouse pharyngeal mucosal tissues. But Yupingfeng San can reduce the expression of ICAM. Consequently， the adjustment mechanism of Yupingfeng San to the upper respiratory Micro-ecological imbalance may be related to the reduce of ICAM.