Abstract: The coconut black- headed caterpillar, Opisina arenosella Walker (Lepidoptera: Coleoptera), is a kind of invasive pest discovered in palm trees in 2013 in Hainan and has caused critical harm and threat to palm trees in tropical and subtropical areas in south China. In order to protect the crop farming development of palm trees, it’ s urgent to screen out some kinds of insecticides which can control it well. The leaf dipping method was used to test the toxicities of 5 insecticides to the third instar larvae of O. arenosella Walker under laboratory conditions. The dead numbers of caterpillars after 24, 48, 72 h were counted separately. The death rate, revise death rate, LC50, the toxicity regression equations, the correlation coefficient and the 95% confidence interval were calculated under different concentrations. The results showed that the order of toxicities of 5 insecticides after 48 h was Dursban (0.82 mg/L)＞Avermectin (0.87 mg/L)＞Beta-cypermethrin (1.55 mg/L)＞Acetamiprid (5.74 mg/L)＞Imidacloprid (10.35 mg/L). LC50 of Avermectin and Dursban to the caterpillar after 24 h and 48 h were the lowest, they were 3.69, 0.87 mg/L and 5.67, 0.82 mg/L, indicating that those two insecticides had the highest toxicity to the caterpillar. Although Imicacloprid had the highest LC50 after 72 h, it was the lowest after 24, 48 h of the 5 insecticides, suggesting that the caterpillar had poor sensibility to Imicacloprid. Therefore, Avermectin and Dursban were recommended as the best pesticides for controlling the caterpillar. The results could be used to provide reference for the prevention of O. arenosella Walker in the field.