In order to solve the problems of near fertilizer accumulation and local ridging in the existing side throw device for organic fertilizer with inclined opposite discs，combined with the function and working principle of each component of side throw device，an auxiliary roller with symmetrical spiral blade was innovated on the basis of theoretical analysis，the key structural parameters and operating parameters were optimized，and the spatial position relationship between the side throw device and the discs of the main throwing component was clarified. Single factor and response surface experiments were carried out by EDEM software，the effects of roller speed，helix angle and blade number on uniformity coefficient of variation and fertilizer proportion within 1m were studied，the optimal parameter combination was obtained after optimization. The simulation results showed that the optimal parameter combination of auxiliary roller was roller speed of 2238r/min，helix angle of 42.70°，number of blades of 4，coefficient of variation of uniformity of 24.45%, fertilizer proportion within 1m of 24.96%，and the simulation results with this parameter combination were better than those with the optimal parameters of the original roller. Test results of new auxiliary roller after innovative design were 25.46% and 25.65%，which were greatly improved compared with 46.77% and 65.94% of the original auxiliary roller，when combined with the main discs throwing uniformity was good, no accumulation and ridging phenomenon occurred. The results showed that symmetric spiral blades can effectively correct the movement direction of fertilizer particles，so that the non-controlled fertilizers concentrated in the main discs were dispersed on both sides. Combined with the main disc and other auxiliary components，the throwing performance was greatly improved.