The complex structure on the spherical-top of flat-fan nozzle orifices and the erosion situation of solid pesticide on the inner surface of nozzle were studied. Firstly, a mathematical equation of the basic structure was established according to the solid geometry. Secondly, the most significant wear in the x-axis of the spherical-top of fan orifices was concluded through mechanical analysis. Finally, the theoretical analysis was verified through the experiments, and the wear rate relationship was established with the spraying time and the dimensional change of the spherical-top of flat-fan orifices. 