Abstract: In order to enhance the quality factor (Q) of micro-electro-mechanical system (MEMS) resonator, this paper proposes an energy-decoupling frame structure which is applied in an MEMS resonator for energy decoupling and Q enhancement. An aluminium nitride (AlN) piezoelectric resonator is designed to work at 30 MHz frequency (f) in the lateral-extension mode. The resonator Q is significantly enlarged to 4.3×10⁴ and the value of f·Q reaches to 1.29×10¹². The energy coupling between the resonator and the substrate is effectively reduced by controlling the resonant frequency ratio of the resonator to the frame structure in around 10:1. Both theoretical analysis and finite-element analysis (FEA) simulation show that the energy loss reduction and Q enhancement of resonator can be achieved by using the proposed structure.