The invention discloses a tunnel ventilation shaft supporting structure and a construction method thereof, belongs to the field of tunnel engineering, and aims at saving the ventilation shaft supporting process, accelerating the shaft building speed and improving the safety. The ventilation shaft supporting structure comprises a ventilation shaft head section, a shaft bottom section and a shaft body section, wherein an annular closed shaft body lining layer is arranged on the inner wall close to the shaft body section, the shaft body lining layer adopts a molded concrete structure, and the shaft body lining layer forms a single-layer lining structure of the shaft body section. According to the invention, a single-layer lining structure is adopted, so that the structure is simplified, the construction process is saved, and the construction period is greatly saved; the molding structure and the shaft forming are simultaneously carried out, so that the mechanization degree is high, and the construction safety is high; and the single-layer lining structure can support surrounding rocks in advance, so that the safety of the ventilation shaft and the construction is improved. The construction method has the advantages of high shaft-forming speed and safe working face.