A plant (2) for building tyres comprises a system for managing initial components (3); a system for managing the manufacturing of semi-finished products (4) starting from one or more initial components; a system for managing the building of a green tyre (5) starting from one or more semi-finished products; a system for managing the curing of said green tyre (6). The logical set of a control unit (8) for the plant (2) and/or of one or more from among control units (8a-8e) for the management systems (3-6) and/or of a automatic visual control system (7) is programmed for controlling at least two parameters, assigning to each of these a quality index (I), discarding a tyre being processed when a quality index (I) corresponding to said discard level (5) is assigned to at least one of said parameters and feedbacking the control result of at least one parameter in order to verify the quality index (I) of the parameters.