Sexual dimorphism is a widespread phenomenon within mammals, and males are generally larger than females. In contrast bats reveal a characteristic female-biased sexual dimorphism, females are larger than males, but its driving mechanism is still unclear. In order to explore the mechanism of sexual dimorphism within Harpiocephalus harpia, 32 specimens were sampled during bat surveys from seven sites in Guangdong, Guangxi, Jiangxi, Hunan, Hainan, Hubei and Zhejiang provinces. All specimens were deposited in Key Laboratory of Conservation and Application in Biodiversity of South China, Guangzhou University. Through multivariate statistical analysis of craniodental and wing characteristics, we examined absolute differences and relative differences after controlling for disparities in forearm length. Significant differences between sexes were evident only in skull, in the teeth and zygomatic breadth. Comparisons of the rest of the craniodental indices, wing measurements and estimated wing areas were not siginficant. The result favors a “Resource Competition Hypothesis” rather than a “Big Mother Hypothesis”. In addition, 12 specimens of H. harpia were collected from Hubei (3 males, 2 females) in July and from Zhejiang (2 males, 5 females) in August, 2017, represent new distribution records from the provinces, which adds to the accumulation of basic biological data of the rare species in China.