[Background] Bacillus thuringiensis (Bt) is a Gram-positive bacterium that is used as a biological pesticide world-wide. Cry1Ac gene from Bt has been commercialized since 1997, and has been able to control cotton bollworm and pink bollworm. However, Cry1Ac gene is not as good to control Spodoptera exigua, Prodenia litura, Pyrausta nubilalis, etc. Therefore, it is necessary to search for a new gene isoform of Bt to control these pests.[Method] Different concentrations of Cry1C were added to the surface of artificial diet of these three insects and bioassays were conducted in the laboratory. The control received no Cry1C artificial diet. Mortality was recorded at 1, 3, 5 and 7 d.[Result] The results showed that mortality of A. caterpillar and P. litura increased gradually with increases in concentration and treatment time of Cry1C. At the 10 μg·mL^-1 Cry1C, mortalities of A. caterpillar and P. litura were 100% and 85.42%. A. caterpillar was more sensitive to Cry1C than P. litura. However, O. nubilalis and Helicoverpa armigera were not sensitive to Cry1C.[Conclusion and significance] Cry1Ac may be a valuable candidate gene for controlling A. caterpillar and P. litura, but ineffective on O. nubilalis and H. armigera. This study provides a new Bt gene type that can be used to control the different insect pests on the cotton plant.