CDAG1 is a novel organ-sized associated gene firstly identified in cauliflower. CDAG1 ectopic overexpression could result in bigger organ size then increase biomass. CDAG1 plays its roles in organ size control by regulating both cell number and cell size. CDAG1 may function in ethylene-mediated signal pathway. CDAG1 is an ideal gene resource in breeding high-yielded crops.