The invention discloses rice and wheat straw smashing and throwing machine, and belongs to the technical field of agricultural machinery. The rice and wheat straw smashing and throwing machine comprises a rack, a side plate, a tensioning wheel assembly, a suspension bracket, a support rod, a side belt assembly, a machine cover and a regulating roller; the suspension bracket is installed on the rack, the rack is further provided with a gear case assembly, the gear case assembly is connected with the side belt assembly through a shaft, the side belt assembly is connected with a smashing knife shaft, the smashing knife shaft is provided with fixed bent knives and straight flail knives, the straight flail knives are fixedly arranged among the fixed bent knives, and every two straight flail knives are installed between the two corresponding fixed bent knives; the machine cover is provided with transverse stationary knives and longitudinal stationary knives, every two longitudinal stationary knives are arranged over the two corresponding straight flail knives, and the fixed bent knives correspond to the transverse stationary knives; the rack is further provided with a straw gathering segment, the back portion of the straw gathering segment is provided with a straw mean-cutting segment, and the straw mean-cutting segment is provided with a mean-cutting plate. The rice and wheat straw smashing and throwing machine is mainly applied to agricultural straw smashing.