[Aim] Leptinotarsa decemlineata is a pest in China according to the National List of Agricultural Plant Quarantine Pests. After its introduction in Xinjiang, it caused considerable losses to the country's potato industry. Examining predation of L. decemlineata eggs and young instar larvae by adult Arma chinensis provides an effective basis for the use of natural enemies to control L. decemlineata. [Method] The experiment was conducted in growth chambers using an indoor feeding observation method. The experimental results were fitted using the HollingⅡ model pattern, and foraging efficiency was calculated. [Result] Arma chinensis adults can prey on L. decemlineata eggs and young instar larvae, and the predator functional response of A. chinensis adults to L. decemlineata eggs and young instar larvae approximated the HollingⅡ type. The predator functional response equations of A. chinensis adults to L. decemlineata eggs and young instar larvae were N_a=0.2862N/(1+0.0198N) and N_a=0.8400N/(1+0.0709N), respectively. Within a certain range, predation of L. decemlineata eggs and young instar larvae by A. chinensis adult increased with increasing density. When the density of L. decemlineata eggs and young instar larvae reached 20, respectively, predation by A. chinensis adults was at the highest rate. The maximum daily predation numbers of L. decemlineata eggs and young instar larvae by A. chinensis adults were 14 and 12, respectively, and the attacking efficiency was 0.2862 and 0.8400, respectively. The predation capacity of A. chinensis on L. decemlineata eggs (4.1299) was lower than that of young instar larvae (9.9526). [Conclusion] A. chinensis adult is a promising predator of L. decemlineata eggs and young instar larvae, however, at different respective control capabilities.