The invention discloses a rectangular piece optimization and stock layout method based on plate utilization rates. The rectangular piece optimization and stock layout method based on the plate utilization rates includes the steps that according to basic parameters of plates and rectangular pieces, the utilization rates of the plates corresponding to the rectangular pieces in the width direction and in the length direction are determined; according to the utilization rates of the plates in the width direction and in the length direction, first rectangular pieces laid on a first piece of plate are determined; and whether the first rectangular pieces are completely laid or not is judged, if yes, whether the first piece of plate has a remaining plate or not except the first rectangular piecesis judged, if yes, according to the width and the length of the remaining plate, the utilization rates of the remaining plate corresponding to the rectangular pieces in the width direction and in thelength direction are calculated, and if no remaining plate exists, layout of a second piece of plate is performed. Due to the method, the utilization rates of the plates are increased, and raw materials are saved.