After 53 (28 ♂♂, 25 ♀♀) adults of the Ornamented Pygmy Frog (Microhyla fissipes) had been collected from Mengla County of Xishuangbanna Dai Autonomous Prefecture in Yunnan Province, China, 16 morphological characteristics of them, such as body length, head length, head width, body mass and female’s brood amount had been measured. With the independent sample t test and covariance method, sexual differences of the all morphological characteristics of this frog have been tested, and the correlation between local morphological characteristics with body length of male and female adults, also the brood amount with the local morphological characteristics of female adults have been also analyzed by the linear regression analysis method. The results showed that, the average body length of female M. fissipes was 25.08 ± 0.40 mm, and the male’s was 24.78 ± 0.31 mm, there was no significant difference in body length and body mass between males and females (P > 0.05, Table 1), the size of male and female individuals was basically identical. All local morphological features were extremely significant positively correlated with body length (P < 0.01, Table 1). Length of lower arm and hand, and hand length were significantly different between males and females (P < 0.05, Table 1), there were also significant differences with the growth rate of body length. Separately, the brood amount was positively correlated with body length, body mass, inter-orbital space, diameter of lower arm, tibia-width, length of foot and tarsus (P < 0.05, Table 2), and extremely significant positive correlation with body mass (P < 0.01, Table 2). Our analyses suggest that, the sexual dimorphism of M. fissipes adults between female and male were mainly manifested in the head width, forearm length and hand length, which possibly related to the ability to obtain food for survivaling, and the success rate of males in competing for mating rights. However, individuals of female may increase their reproductive output by increasing their body length and body weight correspondingly increasing abdominal volume, which was consistented with the fecundity selection hypothesis.