Based on the computational fluid dynamics software FLUENT, using the standard k-ε model, with the cottonseed oil as medium, the numerical simulations of the cavitation flow fields in Venturi tubes were established. The cavitation number and the distribution of gas-holdup of the cavitation region in the Venturi tubes were computed. The effect of the structure of Venturi tubes on cavitation was researched. The results showed that the structure of Venturi tubes had an obvious effect on the cavitation, the cavitation effect enhanced along with the increase of inlet angle and decrease of the laryngeal length, and the diameter of laryngeal and outlet angle had the best value on the cavitation effect, which provided a support for optimizing the design of the structure of Venturi tubes applied in oils. At the same time, it was found by the verification experiment of the hydrodynamic cavitation of cottonseed oil that the hydrodynamic cavitation had a significant effect on the removing of gossypol, and the removal rate increased along with the increase of inlet angle of the Venturi tube, which indicated that the stronger the cavitation effect was, the higher the removal rate was. The results obtained by the experiments were similar to those by numerical simulation.