In order to solve the problems of winding grass and blocking mud before sowingdue to long stubble remained in farmland after harvesting as well as the heavy clay soil in south of China, a multifunctional rape-planting and grass-covering machine was used to collect and cut the rice stubbles, and then row-controlled throw the chopped rice stubbles. Based on this machine, a row-controlled throwing mechanism for rice straw was designed with an two-way auger and the auger groove.The variation on uniformity of throwing rice straw was investigated by using the experiment device dependent on the speed of auger shaft,feeding rate of rice straw, width of adjustable throwing exit by multi-factor and multi-level orthogonal test. The results show that the speed of auger shaft had the significant effect as well as the gaps between feeding rate of rice straw and the width of adjustable throwing exit. The lowest variation on uniformity of throwing rice straw with 10.4% was obtained under the speed of auger shaft of 218 r/min, feeding rate of rice straw of 1.55 kg/s, the width of adjustable throwing exit of 146 mm.