Microplitis pallidipes is considered an important biotic factor for the natural population of Spodoptera exigua in the field, and volatiles play a crucial role in its host selection and location. We previously found that the larva-amaranth complex exhibits significantly attraction to M. pallidipes. To further investigate the sources and specific volatile compounds that can effectively affect the selection behavior of this parasitoid, Y-tube olfactometer assays were conducted to measure the behavioral responses of M. pallidipes to the bodies and excreta of S. exigua and larvae-damaged amaranth, and the corresponding volatile substances were collected and analyzed with SPME and GC-MS. The results showed that both the damaged amaranth and larvae significantly attracted M. pallidipes (the attraction rates were 67.86% and 65.38%, respectively), while the S. exigua excrement did not. GC-MS analysis indicated that 40, 27 and 32 compounds were identified in the damaged amaranth, the S. exigua larvae and their excrements respectively, consisting primarily of alkenes and alkanes. And 22, 17, and 11 compounds were only detected in those treatments, respectively. In addition, DMNT, methyl salicylate, and methyl benzoate in the infested amaranth were significantly higher than those in S. exigua larvae and their excrements, while α-himachalene in S. exigua larvae was higher than that in the damaged amaranth and the excrement of S. exigua. The damaged amaranth and S. exigua larvae were the main sources of volatile compounds which significantly attract M. pallidipes in larva-amaranth complex.