A high-sensitivity through-hole cantilever beam vibration sensor based on dispersion-turning-point (DTP) optical microfiber coupler (OMC) is studied. First, the axial strain and vibration characteristics of OMCs, and the spectral characteristics of OMCs under the loading of axial strain are theoretically analyzed. Then, OMCs with different diameters are prepared by the melting taper method, and the axial strain experiments are carried out. Experimental results show that the axial sensitivity of the OMC is as high as -35 pm/με when the diameter of the OMC is 1.6 μm and DTP is near 1500 nm, which is about 3.5 times of that of the normal OMC. Finally, the OMC with high axial-strain sensitivity is fixed on a through-hole cantilever beam to construct a high-sensitivity vibration sensor, which is used to detect the vibration signal. Results show that the frequency detection range of the sensor is 30-2800 Hz, the response reaches the highest value at the first-order vibration frequency (52 Hz), and the acceleration sensitivity of the sensor is as high as 85 mV/(m·s^-2) with good linearity under the micro-vibration (0-0.6g) at the flat response area (~40 Hz).