Mixed ventilation indirect cooling tower system and cooling method thereof

The invention discloses a mixed ventilation indirect cooling tower system and a cooling method thereof. The system comprises a shutter, a radiator and a machinery ventilation auxiliary unit arranged on a broadening platform of a hyperbola natural ventilation tower. The machinery ventilation auxiliary unit is arranged around a tower wall of the natural ventilation tower. When a blower fan of the machinery ventilation auxiliary unit is turned on, part of hot air passing through the radiator will enter an air inlet apparatus, be accelerated by the blower fan and rectified by an air outlet apparatus and goes up along an inner wall of the tower into a tower cylinder. The invention has beneficial effects that scale of the cooling system is reduced; the system is flexibly operated and has strongadaptation to load change; influence of environment to the system is improved, such as freeze proof.