【Aim】This study investigated the pathogenicity of Serratia marcescens and/or Aspergillus tamarii against the major pests—Ostrinia furnacalis and Helicoverpa armigera—of maize, aiming to provide candidate microbial resources for biocontrol of these pests in Xinjiang.【Method】Highly virulent strains were initially selected from 11 entomopathogenic strains (bacterial strains OF-YH1, OF-YH2, OF-DM, OF-HM, OF-YR and fungal strains Z6, Z7, Z8, R45, R56, R57), and their lethal effects on third-instar larvae of O. furnacalis and H. armigera were determined, along with an analysis of the synergistic effects of the combined treatment. The strains were identified based on morphological characteristics, physiological and biochemical properties, and molecular biological evidence (16S rDNA/ITS sequences).【Result】The preliminary screening indicated that the bacterial strain OF-YR and the fungal strain R56 exhibited the highest insecticidal activity against O. furnacalis and H. armigera, inducing cumulative mortality rates of 80.00% and 73.33% for OF-YR and 83.33% and 67.67% for R56, after 14 d. The median lethal time (LT₅₀) was 8.182 and 8.023 d for OF-YR and 7.945 and 7.357 d for R56. When the two strains were mixed at a ratio of 1:1, the insecticidal efficacy of the combined treatment was enhanced, with the 9 d cumulative mortality rates increasing to 100.00% and 93.00%, and the mortality rates at 14 d reaching 100% (P<0.05). The LT₅₀ values of the combined treatment against O. furnacalis and H. armigera were shortened to 2.566 and 3.902 d, which indicated a pronounced synergistic effect. The strain OF-YR was identified as S. marcescens, and the strain R56 as A. tamarii.【Conclusion】The combined application of S. marcescens OF-YR and A. tamarii R56 significantly enhanced the pathogenicity against O. furnacalis and H. armigera, demonstrating the potential for development as a composite microbial formulation. This provides a novel technical approach for eco-friendly pest management in maize cultivation.