An ultrasonic atomization core (17), an ultrasonic atomizer, and an ultrasonic electronic cigarette are disclosed. The ultrasonic atomization core (17) comprises an atomization sleeve (1). The atomization sleeve is provided with an ultrasonic atomization sheet (2) and e-liquid guide cotton (3) that communicates the outside with an atomization surface of the ultrasonic atomization sheet (2). The atomization surface of the ultrasonic atomization sheet (2) is a concave surface. The e-liquid guide cotton (3) has a convex surface corresponding to the atomization surface. The curvature of the convex surface of the e-liquid guide cotton (3) is greater than or equal to the curvature of the atomization surface of the ultrasonic atomization sheet (2). The convex surface of the e-liquid guide cotton (3) is in contact with the atomization surface of the ultrasonic atomization sheet (2).