Obligate pollination mutualisms between plants and their seed-parasitic pollinators are known to be one of the most specialized plant-insect interactions. The obligate pollination mutualism between Epicephala moths (Gracillariidae) and Phyllanthus microcarpus plants (Phyllanthaceae) has been documented. P. microcarpus species need to rely on species-specific Epicephala female moths for obligate pollination. At night, a female moth actively collects pollen grains from the host male flower by using unique proboscises equipped with numerous hair, and then deposits them on the female flower; subsequently, the female moth lays an egg by using the specialized acicular ovipositor. The hatched larva consumes only a subset of the maturing seeds within a single fruit to complete its development and drills out of the fruit. The rest of the seeds ensure the reproduction of the host's offspring. The floral scent has been considered to be the key signal guiding obligate pollinators to locate host plants in nursery pollination mutualisms; however, studies on floral volatiles of P. microcarpus are lacking. In this study, the chemical composition of floral volatiles of both female and male flowers from P. rmicrocarpus was analyzed using the dynamic headspace technique and gas chromatography-mass spectrometry (GC-MS). Whether there are qualitative differences in floral scent between the sexes of P. microcarpus was determined by conducting principal component analysis (PCA). The results showed that (1) a total of 17 compounds were detected and identified from the floral scent of P. microcarpus, which were dominantly terpenoid and aliphatic compounds. (E)-β-Ocimene was found in the highest amounts in both female (26.77%) and male flowers (17.97%) and was thus considered as the major scent component of P. microcarpus. Of the 17 identified volatiles, 12 occurred in both female and male flowers, indicating similar chemical composition patterns of floral scent between both the sexes of P. microcarpus is obviously different from other Phyllanthaceae plants whose floral scent has been identified in the chemical composition of floral scent. (3) Female flowers emitted significantly more amounts of odor than male flowers. (4) The PCA revealed that P. microcarpus species showed qualitative differences in chemical composition of floral scent between male and female flowers, indicating sexual dimorphism in floral scent. These results indicated that the species-specific floral scent of P. microcarpus might mediate the obligate pollinator Epicephala moth to find the host in order to maintain in the high species specificity of P. microcarpus-Epicephala mutualism. The sexual dimorphism in floral scent of P. microcarpus might be an important reason for the host to adapt to the highly specialized Epicephala pollination.