QCM is a kind of high-sensitivity sensor that can be quantitatively analyzed and characterized by establishing the relationship between QCM parameters changes and the measured viscoelastic films. In this paper, based on the constitutive equation of quartz crystal, the QCM equivalent BVD model of the adsorption of viscoelastic film without considering the capacitance effect under gas-phase conditions is derived. An explicit expression of the QCM equivalent parameters and frequency changes regarding the physical properties of the viscoelastic film is given, revealing the physical phenomena of “extra mass effect” in the gas phase caused by the loss modulus and storage modulus of the viscoelastic film. The BVD model derived in this paper has higher accuracy than that of the EBVD model given by Arnau. The results show that the model can be applied to analyze the characteristics of gas phase viscoelastic films.