The invention discloses a speed change gear of an automatic skin cleaning bath instrument, and relates to a bath head. The speed change gear comprises a first same-speed ring, a second same-speed ring and a third same-speed ring; the first same-speed ring includes an outer tooth A, an inner tooth, three small gears, a ring gear A, pin shafts and two glands C; the outer tooth A is arranged on the outer side of the gear ring A; the inner tooth is arranged on the inner side of the gear ring A, and is engaged with the small gears; the pin shafts are respectively arranged in the center positions of the three small gears; the two glands C are respectively positioned on the upper and lower two surfaces of the gear ring A; the second same-speed ring includes a gear ring B, an outer tooth B, an inner tooth, three small gears, pin shafts and two glands B; the outer tooth B is arranged on the outer side of the gear ring B; the inner tooth is arranged on the inner side of the gear ring B; as the outer tooth A, the outer tooth B and an outer tooth C rotate with the same speed, an inner ring, a middle ring and an outer ring of the bath head also rotate with the same speed; and when the three rings of the bath head rotate with the same speed, the bath effect is greatly improved, and more convenience is brought to users.