Abstract: Jet mixing apparatus has the advantages of online mixing and environmental protection. Because the mixture ratio of single-stage jet pump was too large and unstable, two-stage jet mixing apparatus was developed for meeting the requirements of plant protection machinery. Tests were carried out with different diameters of the main and auxiliary nozzles and distance of the main and auxiliary pipes. The authors obtained change law for pressure and mixture ratio of two-stage jet mixing apparatus. The experimental results provide the basis for apparatus design.