A system for feeding preforms to a container blow-molding machine includes a sorting and alignment device fed with randomly arranged preforms and parallel alignment rollers that rotate about their respective axes and arrange the preforms in conveyance tracks inclined with respect to the horizontal. The system includes elements for removing the incorrectly positioned preforms, which are individually laid flat and arrive from the alignment rollers on the conveyance tracks and are oriented parallel to the longitudinal advancement direction. The removal components include an upper guide having a flow control portion arranged at least in one active blocking position thereof, above the end of the alignment rollers proximate to the conveyance tracks distanced from the alignment rollers to allow passage below the flow control portion of the correctly oriented preforms and block the longitudinal end.