As the independence of consumers in consumption enhances, traditional pharmacies are facing transformation, and become chain stores. The traditional pharmacies have closed shelf display, but chain pharmacies have open shelf and able to meet all of consumers? needs. Therefore, this research studied the relationships among the consumers? knowledge, attitude, situational influence, and consumer behavior in chain pharmacies, and examined the variables of lifestyle, demographic statistics, and consumption behaviors, in order to find out the effects of the consumers? knowledge, attitude, and situational influence on the consumer behaviors. The ?structural equation modeling? was used to validate the cause and effect relationship of the model. The results showed that: 1) The situational influence can directly affect the consumer behaviors. 2) The situational influence can directly affect the consumers? attitude. 3) The situational influence can indirectly affect the consumer behaviors through the attitude. 4) The consumers? behaviors can have significant effect on the consumer behaviors. 5) The consumers? knowledge has insignificant effect on the consumer behaviors, as well as the indirect effect through attitude. Based on the above results, the consumption behaviors of chain pharmacies have less rational consumption knowledge, but do not affect the consumer behaviors. The perceptual situational influence has significant effect on the consumer behavior, indicating that the operation of chain pharmacies should focus on perception instead of rationality.