This paper reports a novel quartz crystal microbalance(QCM)humidity sensor.First,the urea-formaldehyde resin(UFR) polymer was synthesized in alkaline conditions,and then the polymer was prepared in situ by polymerization on the quartz crystal electrode in acidic conditions to form the sensitive layer of the humidity sensor.The influence of film thickness on the detection of sensitivity,the characteristics of response,repeatability,stability of the sensor were also investigated.Experiment results indicated t...