The invention discloses a QCM (quartz crystal microbalance) formaldehyde sensor with chemical and physical adsorption effects and a preparation method thereof, belonging to QCM formaldehyde sensors in the technical field of gas sensors. A sensor substrate is a QCM, and formaldehyde sensitive films 4 with chemical and physical adsorption effects are deposited on two sides of a QCM electrode, respectively, wherein the sensitive films are composite sensitive films prepared from organic polymer sensitive materials and carbon nano tubes or graphene and other materials through processes such as gas blowout, dispensing or ink-jet printing. According to the sensor, the high specific surface area and supporting characteristics of materials such as the nano tubes or graphene as well as adsorption or specific response performance of polymer materials are fully utilized, chemical / physical enhancement effects of double-sided composite sensitive films are exerted, and the sensitivity and adsorption / desorption rate of the sensor are improved. The sensor has the advantages of simple preparation process, low cost, high sensitivity, capability of operating at room temperature and the like and the technical scheme disclosed by the invention can be widely applied to QCM formaldehyde sensors.