Venturi tubes are widely used as feeders in pneumatic conveyance systems because of their effect of accelerating gas flow in the tube and sucking the material from the feed port. Based on the principle of Venturi effect, a Venturi fertilizer tube for use in a side-deep fertilization device with the pneumatic conveyance system in rice paddies was designed in this paper. The airflow field in the new Venturi fertilizer tube was then simulated to test its effect of accelerating gas flow and its ability to suck fertilizers from the feed port, using the computational fluid dynamics (CFD) software, Fluent. The key structural parameters of the Venturi fertilizer tube are as follows: airflow inlet and outlet diameter (21.6 mm), contraction angle (21°), diffusion angle (8°), throat diameter (15.12 mm), throat length (15.12 mm). The simulation results showed that the maximum velocity at the throat section and the diffusion section in the Venturi fertilizer tube is 52.03 m/s, and the maximum velocity at the outlet is 40.8 m/s, which is 2-3 times the velocity of the airflow inlet. This clearly illustrates the acceleration effect on the gas flows. There is also a weak airflow movement from top to bottom generated by differential pressure at the feed port, and the maximum gas velocity is 5.8m/s at the bottom of the feed port. Therefore, the Venturi fertilizer tube can draw the fertilizers from the feed port by suction. In conclusion, the behavior of the Venturi fertilizer tube designed in this paper is consistent with the principle of Venturi effect, which verifies the rationality of its structural design. This research provides guidelines for designing the structure and optimizing the design parameters of a Venturi fertilizer tube in a side- deep fertilization device with the pneumatic conveyance system for rice paddies.