The invention provides a centrifugal impeller and a gas compressor. The centrifugal impeller comprises an impeller disk. The impeller disk comprises a center part and an edge part. The center part can be arranged on an impeller shaft in a sleeving manner, the impeller shaft is provided with a center axis, and the center part is provided with a first end portion located at the rear end and a second end portion located at the front end. The edge part is arranged on the periphery of the center part in an annular manner, the surface, close to the first end portion, of the edge part is an impeller back of the impeller disk, a bulge loop is arranged on the impeller back, the impeller back is a rotative surface formed in a manner that a first generatrix rotates around the center axis, the first generatrix comprises a vertical line, a first arc, a first curve and an extension line, and the vertical line is used for forming the bulge loop. One end of the first arc is connected with the first end portion in a smooth transition manner, and the first arc is concaved in the direction close to the second end portion. One end of the first curve is connected with the other end of the first arc in a smooth transition manner, the other end of the first curve is connected with one end of the vertical line in a smooth transition manner, and the first curve is concaved in the direction close to the second end portion. The extension line is connected with the other end of the vertical line in a smooth transition manner.