This article presents comprehensive studies of carbon monoxide (CO) responses of bare and iron doped six calix[4]arene derivatives substituted with various functional groups based on quartz crystal microbalance (QCM) technique. The functional groups in calixarene molecules were chosen to increase the affinity towards CO. The sensitive films were prepared by using drop casting method on a QCM gold electrode with resonance frequency of 7.995 MHz. The responses of bare and Fe doped calixarene molecules were investigated in details. Our QCM results showed that although both bare and Fe doped calixarene molecules are very sensitive to CO gas and Fe doped calixarene molecules have higher affinity to CO about 27.88 times greater than bare are. Therefore, these results open an approach to create new materials for the gas sensing applications.