In order to reduce the working power of tillage implement, made a combination of the down-cut rotary tillage and the up-cut rotary tillage applied on small agricultural machine is proposed. SPH method is applied to the three-dimensional numerical simulation for rotary soil process of rotating, and thus draws the force characteristics of rotary cutting tools under the different parameters. Combining with the simulation data of the up-cut rotary tillage, the work of tool matching is done. So it can make the force of the up-cut rotary blade and the down-cut rotary blade offset respectively. Accordingly, the small agricultural machinery can reduce energy consumption and improve efficiency. Based on these methods, we develop the small farming machinery which is fit for farming in compacted soil. The data and analysis program based on the study are of great significance for the small farming machine.