Abstract: Enhanced crop genetic diversity is beneficial to crop pest control. Here, we designed a mixture cropping system with 3—4 rice varieties and a monoculture system with a single rice variety to investigate effects of crop genetic diversity on density of the brown planthopper (BPH) Nilaparvata lugens and predatory spiders, BPH biotypes and expression levels of the vitellogenin (Vg) gene. BPH density decreased significantly in the mixture cropping system compared with the monoculture system, up to 98.29% at the most, while spider density increased in general in the mixture cropping system. With rice growth, proportion of less damaging BPH biotype I showed a gradual increase in the mixture cropping system, while expression level of Vg gene in the mixture cropping system decreased gradually, being significantly different in the middle and late developmental stages of rice plants compared to the monoculture system.