The invention discloses a fresh air device for a suspended sash window. The device comprises a fresh air device body, a window frame hook and loop fastener, a suspended sash window hook and loop fastener, a weatherproof cloth and a sealing zipper; the fresh air device body is installed on a window frame, the window frame hook and loop fastener is installed at the inner side of the window frame, the suspended sash window hook and loop fastener is installed at the inner side of the suspended sash window, and the weatherproof cloth is installed between the window frame and the suspended sash window; an air inlet extension pipe on the fresh air device body penetrates through the weatherproof cloth; the fresh air device body comprises a fresh air filtering device, a top plate, a clamping edge,an air inlet, the air inlet extension pipe and an air outlet, the top side of the fresh air filtering device is provided with the top plate, one side of the top plate extends and is provided with thefresh air filtering device, and the clamping edge is arranged at the tail end of the top plate and extends downwards; the top side of the fresh air filtering device is provided with the air inlet extension pipe, and the tail end of the air inlet extension pipe is provided with the air inlet; the air outlet is formed in the front side of the fresh air filtering device. The fresh air device for thesuspended sash window has the advantages that the manufacturing and application cost is reduced, punching installation is not needed, and the device is convenient to install and move and high in sealing performance and capacity.