Abstract: Gel electrophoresis was used to study the performance of Peroxidase isozymes in a po- pulation of 46 individuals from selfing the BCF₁ (Back Crossing F₁) between the Cucumis×hytivus Chen and Kirkbride (an amphidiploid species obtained through interspecific hybridization between C.hystrix and C.sativus) and C.sativus L.Great variations were observed in the patterns among the population.Base on the differences in number and location of the bands the individuals were divided into 6 groups,indicating genetic polymorphisms in the population.Comparing the patterns,the population produced 4 new bands;the average number of bands in the population is 7.8,which is 56.0% higher than that in cucumber (5.0).Meanwhile,the activity of bands varies great among the population.The results demonstrated that the genetic base of cucumber has been dramatically widened through the backcrossing with C.hytivus.