Odorant binding proteins (OBPs) are required for olfaction perception, and thus may be possible targets for controlling the population of pests by interfering with their chemical communication. A single OBP LmigOBP1 has been identified in the antennae of Locusta migratoria, though four isoforms have been detected. Here, we have investigated the ligand-binding specificity of LmigOBP1 using 67 volatile odor compounds. Fluorescence assays indicate that LmigOBP1 does not bind fecal volatiles or green leaf odors, but shows high affinity for some linear aliphatic compounds, with pentadecanol and 2-pentadecanone being the strongest binding ligands. A 3-dimensional (3D) model of LmigOBP1 was built by homology modeling. Docking simulations based on this model suggested that Asn74 of LmigOBP1 is a key binding site, and this was validated by site-directed mutagenesis and fluorescence assays. We suggest that, as a general rule, a hydrophilic amino acid at the entrance of the binding cavity participates in initial recognition of ligands, and contributes to ligand-binding specificity of OBPs.