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In this paper, a fifth-order fully differential interface circuit ( IC) is presented to improve the noise performance for micromechanical sigma-delta (Σ-Δ) accelerometer. A lead compensator is adopted to ensure the stability of the closed-loop high-order system. A low noise capacitance detection circuit is described with a correlated-double-sampling ( CDS) technique to decrease 1/f noise and offset of the operational amplifier. This paper also proposes a self-test technique for the interface circuit to test the harmonic distortion. An electrostatic force feedback linearization circuit is presented to reduce the harmonic distortion resulting in larger dynamic range ( DR) . The layout of the IC is implemented in a standard 0?6 μm CMOS technology and operates at a sampling frequency of 250 kHz. The interface consumes 20 mW from a 5 V supply. The post-simulation results indicate that the noise floor of the digital accelerometer is about -140 dBV/Hz1/2 at low frequency. The sensitivity is 2.5 V/g and the nonlinearity is 0?11%. The self-test function is achieved with 98?2 dB third-order harmonic distortion detection based on the electrostatic force feedback linearization.