The invention belongs to a plant protection field, and especially relates to an insecticidal composition containing chitosan oligosaccharide, wherein the composition, beside Chitosan oligosaccharide, further contains one selected from cyantraniliprole, flubendiamide, flonicamid, chlorantraniliprole and thiamide, a mass ratio of chitosan oligosaccharide to another effective component is 0.1:1-50, and the composition can be prepared to be a suspending agent, a particulate agent, a wettable powder, a water dispersion granule, a micron emulsion or an emulsion in water. The insecticidal composition is used for controlling lepidoptera pests or homopterous insects, and has excellent control effects on diamondback moth, cabbage caterpillar, prodenia litura, rice leaf roller and apple skin worm.