A uniform light generating system for adjusting output brightness, including a light-generating unit, a light-transmitting unit, a hollow spheroid unit, a light-sensing unit, and a control unit. The light-generating unit has a light-emitting element for generating light beams and a brightness control element for adjusting the luminous flux of the light beam. The hollow spheroid unit is communicated with the other side of the light-transmitting unit for guiding the light beams into an external casing of the hollow spheroid unit. The light-sensing unit detects electric power values in the external casing. The control unit is electrically connected to the light-generating unit and the light-sensing unit. Thereby a user can obtain a real illumination value via adjusting the illumination values of the light beams that are projected from the hollow spheroid unit.