【Aim】 This study assessed the control effect of Arma chinensis on Leptinotarsa decemlineata and provided a theoretical basis for the biological control technology of L. decemlineata. 【Method】 This study was conducted by setting up and releasing larval A. chinensis at different ages (3rd, 4th, 5th, and adult) according to the same benefit-to-harm ratio (1∶15) and observed the population variation of L. decemlineata during the incubation period, in potato fields. 【Result】 According to the weekly survey of the number of infestations of each covered L. decemlineata, the rate of infestation reduction of the 3rd, 4th, 5th instar nymphs, and adults treated by the treatment group was higher than that of the control group one week after release, indicating that both the 3rd to 5th instar nymphs and adults of the L. decemlineata had evident predation ability on L. decemlineata. After one week of release, the results showed that the results of adult treatment reached 61.26%, which was significantly better than that of the other treatment groups (P<0.05). The results of adult treatment reached 100%, 97.19% at the 5th instar nymphs, and 96.92% at the 4th instar nymphs, at the 6th week with no significant difference between the three groups (P>0.05), and were significantly faster than that of 88.24% at the 3rd age (P<0.05). The yield of potatoes treated with biological control of A. chinensis was significantly higher than that of the control group (P<0.05). The tuber number per plant and weight per plant of potato treated with biological control of A. chinensis were significantly higher than those of the control group (P<0.05). When A. chinensis was released for one day in the field, the L. decemlineata population decreased except for the control group. In addition, the decrease in the population in the adult treatment group was significantly higher than that in the other treatment groups at 21 days (P<0.05). The control effect of the adult treatment group was 40.25% higher than that of the 5th treatment group at 21 days and significantly higher than that of the 4th and 3rd treatment groups (P<0.05). 【Conclusion】 In the shroud, the adult and the 5th instar treated the L. decemlineata briefly, and the damage control effect was significantly better than that of the other treatment groups. The population of L. decemlineata can be controlled at a lower level by releasing adult A. chinensis in the field.