This study examined how plant diversity in grasslands affects parasitic Hymenoptera and Coleoptera populations. The results showed: 1) Plots with a mixture of legumes, herbs, and grasses supported greater abundances of parasitic Hymenoptera and Coleoptera than single species plots. 2) Parasitic Hymenoptera can effectively predict overall arthropod diversity in agroecosystems, and increasing plant diversity may lead to more diverse invertebrate communities and improved ecosystem services. 3) Multi-species plant swards have potential to transform agricultural grasslands into more biodiverse systems.