The invention relates to a sand ultralow-frequency vibration sensor based on a lens-contained fiber array. The sensor is composed of an optical fiber array probe part, an optical branching and combiner part, and a light source and photoelectric detector part. The optical fiber array probe part consist of a first multimode fiber, a first lens fiber, a second multimode fiber, a second lens fiber, a third multimode fiber, a third lens fiber, a fourth multimode fiber, and a fourth lens fiber. The optical branching and combiner part includes a 1*4 optical branching unit, a second 2*1 optical combiner, and a second 2*1 optical combiner; and the light source and photoelectric detector part includes a light source, a first channel of a photoelectric detector, and a second channel of the photoelectric detector. According to the invention, because of the special arrangement way of the fiber array and the high light receiving capability of the tapered-lens-based fiber, detection of ultralow-frequency motion characteristics of small-sized particle objects like sands and PM2.5 particles can be realized.