In this study, we tested the effect of a range of insect orders including Trichoptera as outgroups for lepidopteran phylogeny. Phylogenetic analyses performed with four different partitioning schemes using the maximum-likelihood method provided four different topologies (T1-T4) and topological test most supported T1 topology. When the means of first principle component for nucleotide frequency between A/T and G/C of PCGs was considered Trichoptera, Diptera, Coleoptera, and Orthoptera tended to result in T1 topology more frequently in the given ingroup taxa and outgroups tested. This result contradicts to the general view that the sister taxon might be the best outgroup. The T1 topology was largely consistent with a recent large molecular dataset-based lepidopteran phylogeney, presenting the relationships ((((((((((Noctuoidea + Geometroidea) + (Bombycoidea + Lasiocampoidea)) + Drepanoidea) + Mimallonoidea) + Pyraloidea) + Gelechioidea) + Papilionoidea) + Tortricoidea) + (Gracillaroidea + Yponomeutoidea)) + Hepialoidea).