Since the instability of dangerous rock mass exhibits as the sudden collapse of destruction

no obvious displacement characteristics can be identified. Thus

the application of conventional displacement monitoring techniques is difficult to achieve the purpose of monitoring and early warning. In addition

the stability of dangerous rock mass is influenced by the bonded area between dangerous rock block and bedrock

which is considered as one of the critical parameters. However

this bonded area is hard to obtain

which makes it difficult to evaluate the stability of the dangerous rock block. In this study

we assume that the rock block is homogeneous and isotropic

the main control structural plane is a single plane

the damping ratio of the system is less than 1 and the deformation is linear elastic deformation within the amplitude range. As a result

the vibration model of the dangerous rock mass can be simplified as a spring oscillator model. Then

the relationships among the natural vibration frequency of dangerous rock mass

the bonding area

the elastic modulus and the quality of dangerous rock mass were established by the theoretical derivation. Considering the limit equilibrium model

a new model based on natural vibration frequency was derived to evaluate the stability of dangerous rock mass. A dangerous rock block on the right bank of Baihebao reservoir was selected as the case study. A wireless vibration sensor（micro core） was fixed on the dangerous rock block to acquire data

which was converted to natural vibration frequency by the Fourier transform and other mathematical methods. Furthermore

the bonded area was determined according to the relationship among natural vibration frequency

rock block bonding area and elastic modulus. Finally

the stability evaluation of dangerous rock mass was completed using the new model. This case study verifies the feasibility of the proposed procedure with a faster rate and more accuracy than traditional methods.