A new concept is introduced that characteristic damping coefficient kc is used to distinguish between the effects of mass loading and liquid damping of a quartz resonator vibrating in liquids. It is derived that the value of kco has nothing to do with the properties of liquid and solid deposited on the quartz crystal. It only depends on the parameters of the crystal resonator

such as fundamental frequency

the area of the electrode and the overtone number.The effect of mass loading occurs only when kc varies. By measuring the frequency and amplitude simultaneously

the influence on kco of fundamental frequency

electrode area and overtone number of a 10MHz AT cut quartz crystal resonator is studied.The experimental results fit the theory well.