Abstract: For the problem of uneven mixing in the traditional mixing process, a horizontal plant protection mixing machine was designed and its mixing uniformity was simulated. First, the key components of the medicine mixing machine were designed. The horizontal plant protection medicine mixing machine was mainly composed of a water delivery device, a medicine delivery device, a medicine mixing device, and a walking device. The power of the agitator was 6 W and the diameter of the mixing shaft was selected as 30 mm. Based on the above design, the simulation test for the uniformity of the medicine was carried out. The experiment explored the influence of the structural parameters（number of inlets and number of blades） of the mixer on the flow field, pressure field, and uniformity of the mixture. The results of the study found that the number of inlets and the number of blades of the mixing machine had significant effects on the flow field and pressure field of the liquid medicine. The change of the flow field affected the uniformity of the mixing. The more the number of blades, the more obvious the agitation was inside the fluid. When the number of inlets and leaves was 4, the uniformity of the mixture was the highest. This article provides a theoretical research basis for improving the mixing uniformity of the horizontal mixer.