The present invention discloses an internal-circulating heat dissipation system for a stage light, the system comprising a support arm, a light holder and a circulating heat dissipation system, wherein the light holder is pivotally connected to the support arm through a pivot shaft, the pivot shaft is of a shaft pipe structure, an internal space of the light holder is in communication with an internal space of the support arm through the pivot shaft, the circulating heat dissipation system comprises a cooling medium, a heat dissipation component located inside the support arm, and a power component that promotes the cooling medium to flow in circulation between the light holder and the heat dissipation component through the shaft pipe structure, and the cooling medium is isolated from an external space of the stage light.