Abstract:In this experiment, the polyacrylamide gel electrophoresis is adopted to test the esterase isozyme of seeds and seedling of the fourteen species of related Citrus plants. The relationship with each other is analysed according to the resutls of zymogram and scanning chart. The data show that there are differences of various degrees in the number of the isozyme bands, the enzyme activity, the migration of enzymes and their chromatogram scanning. The isozyme of the same species has different forms of expression in the different period of development. The esterase isozyme zymogram of the Citrus seed is generally stable. It can be used as the biochemical and genetical index to detemine the genetic ralationship of Citrus.