The present disclosure refers to a forming machine based on prohibited positions of discharge of a formed material formed by the forming machine. A forming machine includes: a gathering unit configured to gather in grass of a farm field； a forming unit configured to form the grass gathered by the gathering unit； a discharge unit configured to discharge the grass formed by the forming unit into the farm field； a prohibited position acquisition module configured to acquire a prohibited position at which discharge of a formed material is prohibited； and a control module configured to perform control based on a relationship between a discharge position at which the formed material is discharged from the discharge unit and the prohibited position. Further a grass management system and a method for operating a forming machine are provided.
