The invention provides a pediatric oral cavity dilator and belongs to the technical field of pediatric medical instruments, the pediatric oral cavity dilator comprises a lip supporting mechanism, the lip supporting mechanism is composed of two side lip supports, connecting plates and an arc-shaped connecting strip, the two connecting plates are fixed to the front sides of the bottoms of the two side lip supports respectively, the arc-shaped connecting strip is fixed to the bottoms of the two connecting plates, a fine adjustment mechanism is arranged between the two connecting plates, tooth supporting mechanisms are arranged on the front sides of the two connecting plates, each tooth supporting mechanism comprises a lower connecting rod, the lower connecting rod is fixed to the front side wall of the connecting plate, a bearing is fixed to the upper end of the lower connecting rod, an upper connecting rod is rotationally connected into the bearing, a kidney-shaped sleeve is fixed to the tail end of the upper connecting rod, an upper supporting plate and a lower supporting plate are rotationally connected into the kidney-shaped sleeve through two rotating shafts, a spring is arranged between the upper supporting plate and the lower supporting plate, and the whole device is reasonable in structural arrangement, ingenious in conception, flexible and convenient to use, convenient to clean, capable of being recycled, capable of avoiding resource waste and good in child oral cavity opening effect.