The invention discloses a feed sheet positioning ring comprising a positioning ring body which has an elastic structure. A positioning cavity correspondingly matched with a feed sheet is formed in the internal wall of the middle part of the positioning ring body. The positioning ring body is provided with an opening communicated with the positioning cavity. The top surface of the positioning ring body is provided with a first boss. The bottom surface of the positioning ring body is provided with a second boss. The top surface of the first boss and the top surface of the second boss are respectively used for being correspondingly matched with the two clamping parts of the feed sheet in an abutting way. The positioning ring body also comprises multiple convex parts which outwardly protrude from the external wall of the positioning ring body along a diameter direction. The positioning ring body is also provided with at least one arc through hole which is arranged in a way of surrounding the positioning cavity. With application of the feed sheet positioning ring, effective and reliable positioning for the feed sheet can be provided and the feed sheet positioning ring also has a size adaptive function.