The distribution of soil particles and planting tube space position affects reversal cultivated land and fertilization seeder seeding performance. Through the establishment of rotary tiller system coordinate system; Firstly giving the analysis of soil grain not heel cover shell collision and the first meeting with cover shell collisions motion situation, through Matlab found the first meeting with cover shell collisions will collision with spin plow knife again, and calculated separately spin plow knife in a horizontal position, tangent 45 ° direction and in vertical direction of three position of the collision curve. Findly, fitting total soil particle flow distribution curve. According to sow requirements, for agriculture combined machine seeding tube decorate location provides an important basis.