Sensors are one of the important elements of modern mechatronic and robotic systems [1, 2]. Of great interest is the issue of designing small-sized angular velocity sensors, which are widely used in various fields of industry [2, 3]. Among the huge variety of angular velocity sensors, in recent years, more and more attention has been paid to the design of micromechanical gyroscopes (MMGs). The main problem of MMG is the high dependence of qualitative indicators on deviations of the geometric and physical parameters of the resonator [4, 5]. The paper considers the issues of determining the splitting of the natural oscillation frequencies of MMG annular resonators caused by a small deviation of the radius of the median surface of the resonator. As a result of the work, an energy method is proposed for calculating the natural oscillation frequencies of an annular resonator, adapted to geometric deviations. Based on the calculation results, it is shown that the largest splitting of the natural frequency is caused by the 2 and 4 harmonics of the radius deviation.