The inertia force sensing characteristics of FBAR(Film Bulk Acoustic wave Resonators) micro- accelerometer sensor are studied, which integrates inertial force sensing structure of silicon micro mass-proof and cantilever beams with AlN(Aluminum Nitride) FBAR detecting elements. The stress distribution of silicon micro supporting beam under the inertia force loads are obtained by applying Finite-Element Analysis(FEA) static simulation. Then the maximum stress value is selected as load, the relationships between elastic coefficient and stress of wurtzite AlN are calculated according to the first principles. Therefore, the maximum variation of AlN elastic coefficient under the inertia force load can be predicted. Next, the micro-accelerometer frequency characteristics and the tendency of FBAR micro-accelerometer are predicated through the analysis of harmonic response. It is concluded that the resonance frequency of FBAR micro-accelerometer shifts to a higher one under an inertial load, with a sensitivity about kHz/g; and there exists a good linearity in the acceleration increment-frequency shift characteristic curve.