The introduced resonant accelerometer makes use of the equivalent electrostatic stiffness to sense the acceleration. The sensitivity can be adjusted by changing the applied sensing voltage. But the no-linearity problem between the output frequency and applied acceleration is difficult to calculate the sensitivity and analysis its influence directly. When the stiffness of the fold beam is much smaller than the vibrating beam, the analytic sensitivity expression is given. The relationship between the sensitivity and the structure critical dimension is easily obtained in the design stage. A resonant accelerometer with sensitivity of 62Hz/g is designed and fabricated by bulk-silicon dissolved processes. The experiment finds there is the critical dimension loss in the fabrication process, which makes the sensitivity change; the same frequency disturbance will influence the closed-loop phase equilibrium. The equivalent interface model is built for the signal processes in the future. The frequency modulation and re-modulation is suggested to eliminate the disturbance. Vacuum package should be adopt to enlarge the weaken output signal.