The invention provides a pressure sensor and a forming method of the pressure sensor. The pressure sensor comprises a substrate, a second dielectric layer, a first electrode layer and a second electrode layer, wherein the substrate is provided with a device zone and a first dielectric layer is arranged on the surface of the substrate; the second dielectric layer is located on the surface of the portion, in the device zone, of the first dielectric layer and provided with a stepped side wall; the first electrode layer is arranged on the surface of the first dielectric layer and the surface of the second dielectric layer and provided with a stepped zone located on the surface of the stepped side wall of the second dielectric layer and the appearance of the surface of the stepped zone of the first electrode layer corresponds to the appearance of the surface of the side wall of the second dielectric layer and is of a stepped shape; the second electrode layer is located on the surface of the first electrode layer and electrically isolated from the first electrode layer, a cavity is formed between the portion, in the device zone, of the second electrode layer and the portion, in the device zone, of the first electrode layer, and the appearance of the surface of portion, in the cavity, of the second electrode layer corresponds to the appearance of the surface of portion, in the cavity, of the first electrode layer and is of a stepped shape. The sensitivity of the pressure sensor is improved.