Abstract: This study screened Bt strains with insecticidal activity against A. subalbatus and identified the biological functions of these strains to enrich the resource library of mosquito-killing strains. Using 145 Bt strains as experimental materials, methods such as bioactivity determination, scanning electron microscopy observation, and determination of amylase and protease production were employed to screen Bt strains toxic to third-instar larvae of A. subalbatus. After primary and secondary screening, 25 Bt mosquito-killing strains with corrected mortality rates >60% were selected, among which 7 strains exhibited a corrected mortality rate of 100%. Strain Gx0002898 showed the highest mosquito-killing activity, with an LC₅₀ of 4.729 μg/mL. Additionally, scanning electron microscopy observation revealed that most mosquito-killing strains produced large quantities of circular and rhomboid crystals during the spore stage. A total of 24 strains producing amylase and 35 strains producing protease were screened, among which 6 strains showed both high toxicity to Aedes larvae and the ability to produce protease and amylase. This study identified some Bt strains with potential dual effects of mosquito-killing activity and production of protease and amylase, which may have potential for controlling plant diseases, thus providing excellent experimental materials for the development of new microbial insecticides and fertilizers.