Disclosed are an air duct volute (50), an air duct system and an air conditioner. The cross-sectional shape of the volute (50) is designed to be in the shape of a drum. The volute (50) is applied to a cabinet with a cylindrical appearance, such that the shape of the shell of the volute (50) can be matched with a panel (60) of an air conditioner with a circular housing. Compared with a straight volute (10) with a rectangular cross section in the prior art, space in the cavity of the air duct volute (50) is larger than that of the straight volute (10) with the same width. The larger size of the air cavity allows for the selection of larger fan blades (20). When the air conditioner operates, the air supply efficiency is higher, and the noise is lower.