Abstract: Objective To evaluate the toxicity of photoactivated insecticide K-01 to the larvae of Aedes albopictus and observe the histopathological changes in the larvae. Methods The number of dead larvae was recorded after application of K.-01 at different concentrations under different illumination conditions. The content variation of the midgut, malpighian tubules and fat bodies in the larvae was observed microscopically, and the genomic DNA of the larvae was extracted for electrophoresis to identify the target bands. Results The maximum larvae-killing effect was achieved with 50 mg/ml K-01 applied under sunlight (100% killing 24 hours after application). Optical microscopic observation of the killed larvae revealed severe damage of the mid-intestinal cells that showed disintegration and elongation. Distinct vacuoles were observed in the fat body cells, in which red droplets were seen to assemble around the cell nuclei. The result of 0.8% agarose gel electrophoresis of the larvae genomic DNA presented typical ladder patterns, suggesting the presence of cell apoptosis. Conclusion K-01 is an effective photoactivated insecticide.