A heat dissipation structure for an ellipsoidal lamp to provide an improved cooling effect for the ellipsoidal lamp has a redesigned shape and installing location for the blower duct that extends the outlet thereof to the edge of effective light beam zone of the ellipsoidal lamp so that the outlet is most close to the hot spots that require heat dissipation. Airflow ejected from the blower duct also is prevented from scattering to improve heat dissipation effect. The outlet may have a guiding plate located therein to channel the airflow close to the hot spots and match the shape of a reflection hood to improve airflow without scattering.