A Z-axis capacitive accelerometer includes a substrate, a capacitance sensing plate, a proof mass and at least one pair of spring beams. The capacitance sensing plate includes two symmetrical sense areas to create differential capacitive measurement. A decoupling structure separates the proof mass and the capacitance sensing plate and their rotational motions from each other. In the proposed Z axis capacitive accelerometer, the distance of the capacitance sensing plate relative to its rotation axis is considerably increased, thereby effectively enhancing the sensitivity when measuring the Z-axis acceleration.