Aiming at the problems that organic fertilizer is easy to agglomerate in long-term piling up and the existing fertilizer apparatus has poor crushing effect on block organic fertilizer，which is not conducive to mechanized deep construction and difficult to apply fertilizer by strip in farmland. The fertilization method of crushing organic fertilizer by roller differential extrusion was put forward to improve the crushing rate of farm manure，ensure the quality rate of fertilizer and improve the utilization rate of fertilizer. The fertilizer block can be broken and forced to discharge which can be realized at the same time by the relative rotation of the fertilizing roller. By building a test of roll differential extrusion fertilizer apparatus, the key parts of fertilization roller were designed, including tooth roller，tooth profile and roller tooth arrangement，force analysis model of fertilizer fragmentation and the theoretical model of fertilizer amount were set up and the main factors affecting crushing force and key parameters affecting fertilizer amount were got，and then the influence law was produced. A discrete element model of fertilizer fragmentation was built to clarify the rotation speed of upper and lower fertilizing roller of fertilization device and the height difference of the center of fertilization roller and effect of fertilizer amount on crushing rate. The orthogonal rotation experiment of multiple factors was designed to optimize the operation performance parameters of the fertilizer device. The results showed that the rotation speed of the top fertilization roller was 238r/min，the rotation speed of the lower fertilization roller was 374r/min，the height difference between the two fertilization rollers was 71mm，the crushing rate was 80.3%，and the fertilizer dropping rate was 99.2%. In the validation test，four kinds of organic fertilizer with water content ranging from 8% to 40% were selected to verify the optimized parameters. The results showed that the crushing rate was 90.7%，80.8%，79.6% and 76.9% and the fertilizer discharge rate was 95.6%，97.8%，98.2% and 98.6%, respectively. The average error between the results and the optimized results was 4.66% and 1.66%, respectively. The experimental results showed that the roller differential block type fertilizer applicator had high quality of broken fertilizer.