A sensor using ultrasound to detect presence and nature of analyte includes an ultrasonic element and a receptor thereon. The ultrasonic element includes a first electrode, a second electrode facing and spaced apart from the first electrode, an insulating layer between the first electrode and the second electrode, and a vibrating film between the insulating layer and the first electrode. The vibrating film carries the first electrode. A cavity is formed between the vibrating film and the insulating layer. The receptor is on a side of the first electrode away from the second electrode. The receptor can combine with a target substance in a test analyte. When the first electrode and the second electrode are applied with different voltages, certain ultrasound frequencies are generated as the vibrating film vibrates, and the presence and weight of different target substances are indicated by the changes in resonance.