How insect communities are assembled in nature remains largely unknown. In particular, whether habitat filtering or competition serves as the main mechanism in forming insect communities is rarely subject to an in-depth investigation. One bottleneck lies in the difficulty of species identification when dealing with a large number of diverse insects. However, high-throughput sequencing technology coupled with classic DNA barcoding offers a great opportunity to infer community assembly for this speciose group. In this study, using 13,909 full-length barcodes obtained by Sanger sequencing or the full-length metabarcoding method (SOAPBarcode), we showed that competition was the main assembly mechanism for the moth communities in the younger Taihang Mountain, while habitat filtering for those in the old Yanshan Mountain. The two sequencing methods showed highly consistent results with regards to both diversity composition and community assembly mechanism. Significant phylogenetic signals and structure suggested that the focal moth communities were the result of the non-neutral assembly process, which was further confirmed by results of neutral assembly test that accounted for immigration and speciation rates. Our study showed that the full-length metabarcoding method can facilitate community assembly inferences, even for speciose taxonomic groups.