The interval meshing involute gear fertilizer apparatus was designed to solve the problems of uneven discharging of outer-groove fertilizer apparatus. Based on theoretical analysis,the fertilizer discharging process has been simulated by the discrete element method to study the effects of the structural parameters of fertilizer wheel on the uniformity of discharging performance. The orthogonal optimization test using the tooth number,interval and pressure angle of gear tooth of the fertilizer wheel as test factors and the variation coefficient of the uniformity of fertilizer discharging as test index was conducted. The results showed that three factors affecting index was in the order of tooth number > interval > pressure angle. The tooth number had significant influence on the uniformity of fertilizer discharging (P<0.05).The optimal structural parameters of fertilizer wheel included the tooth number of 12,6 mm interval,25° gear pressure angle. The minimum variation coefficient of the uniformity of fertilizer discharging of fertilizer apparatus is 17.59%. The interval meshing involute gear fertilizer apparatus with optimal structure parameters was trial-developed and experimented. The results showed that relative error of the fertilizer discharging mass of the test with theoretical value,simulation value the variation coefficient of the test was -0.95%,-2.41%,and 19.01%,respectively. The results were basically consistent with the simulation result. The variation coefficient of outer groove wheel fertilizer apparatus was 31.96%. The variation coefficient of the test was 12.95 percentage point,smaller than that of outer groove wheel fertilizer apparatus. The results meet design requirements and will provide references for the optimization of fertilizer apparatus.