Seventy-three specimens (♀39, ♂34) of Ranna chaochiaoensis whose snout-vent length was more than 40 mm were collected during April to December of 2006 from a northeast suburb of Kunming. Their snout-vent length, body weight, liver and body fat, weight of ovary and spermary, weight and diameter of oviduct, and diameter of egg measurements were taken. The results were analyzed by ANOVA with the length of the snout-vent (or weight of body) as the covariate factor, showed that there were significant differences in the diameter of the oviduct and egg; weight of liver, body fat, ovary and oviduct in females and weight of spermary in males. The results of the correlation test showed that weight of ovaries had a significant positive correlation with the weight of the liver and oviduct, diameter of oviduct and eggs in females but not with the weight of body fat, which meant that the development of ovary weight corresponded with the development of these organs. The development of ovaries and spermary weight had significant positive correlation in each month, which meant that the development of male sex glands synchronized with that of females. According to the results of dissections, analysis and field observation in the Kunming area, the reproductive time of R. chaochiaoensis finished in October, with an annual reproductive peak. Body fat could supply energy during the development process of sex glands in females. During the developmental process of ovaries, the liver did not supply energy; however, it supplied energy during the process of amplexus and spawning. Compared with females, in males the effect of supplying energy from the liver and body fat was evident during the development process of the sex glands, which meant that little energy was expended. So the reproductive investment of males was less than that of females. Some individual females put off hibernation so they could feed and increase their energy through winter. However, it would cause mortality in adults as the temperature drops dramatically. Newborn tadpoles of R. chaochiaoensis would also face a desolate environment during winter and lack resources during their development and metamorphosis. It would be beneficial for the continuance of the population to protect the environment where R. chaochiaoensis lives during the rothole linked with their life cycle, such as the peak of spawning, hibernation and the dry season when tadpoles develop.