A projection system including a light valve, a lens, an arc reflector, and an arc screen is provided. The light valve is capable of providing an image beam. The lens is disposed in the transmission path of the image beam. The arc reflector has an arc reflective surface. The arc reflective surface is disposed in the transmission path of the image beam from the lens, so as to reflect the image beam. The arc reflective surface is curved in a first direction and not curved in a second direction substantially perpendicular to the first direction. The arc screen is disposed in the transmission path of the image beam reflected by the arc reflective surface. The arc screen is curved in the first direction and not curved in a third direction substantially perpendicular to the first direction. A projection apparatus and an imaging module are also provided.