The blending process of granular multi-fertilizer flows in the nutrient proportion of variable rate technology (NPVRT) lacks mechanism research at present, and the blending cavity structure is the most important factor influencing blending uniformity of a variety of fertilizer. In this paper, using discrete element method, a variety of granular fertilizer, blending and seeding process based on three different blending cavity designs are simulated, and then the multi-fertilizers blending process and its uniformity characteristics are analyzed under three different structures. The computing results and mechanism analysis show that the collision wall shape of blending cavity affects rebound angle and horizontal velocity after particle collision, and both of factors affect the dispersed area of post-collision particles in the blending cavity. B type of blending cavity structure ensures optimum blending uniformity. When fertilizing flow increases, the fertilizer blending uniformity also increases accordingly.