【Background】 Ladybird beetles (Coleoptera: Coccinellidae) are important predators in maize fields and prey on many different agricultural pest insects. They provide an important ecosystem service, and should not be harmed by new agricultural techniques. 【Method】Filed studies were conducted to determine whether transgenic Bt maize, expressing the cry1Ab toxin to control corn borers, has unintended impacts on ladybird beetle species richness, abundance of species and population dynamics of dominant species, with respect to an isogenic hybrid as control. Bt maize and its isogenic hybrid were planted in late of April and middle of June, as spring and summer maize, respectively, at Langfang, Hebei Province, China. 【Result】There were 8 species of ladybird beetles observed, including Propylaea japonica (Thunberg), Harmonia axyridis(Pallas), Coccinella septempunctata(L.), Scymnus (Neopullus) babaiSasaji, Stethorus punctillum(Weise), Scymnus folchinii(Canepari), Scymnus inderihensis(Mulsant), and Anisosticta kabensis(Lewis). Few differences were found in species richness and abundance between the Bt and non-Bt maize fields, either in spring or summer corn field. The dominant species was P.japonica in the spring, and P.japonicaand H.axyridisin the summer, respectively. No significant differences were observed in population dynamics of P.japonica and H.axyridisin spring and summer in the two types of fields. 【Conclusion and significance】Bt corn expressing cry1Ab toxin had no significant effect on the observed parameters, therefore, this Bt maize hybrid may be suitable in an integrated pest management system.