Identifying the patterns of body size, age and growth in relation to environments may help us to understand the evolution of life history of organisms. This study compared the variability in these demographic traits of a temperate frog, Rana chensinensis, among populations from Northern China located at three elevations (567, 1470 and 1700 m) with distinct mean annual temperature (12.1, 5.8 and 3.9°C). Overall, frogs from higher elevations tended to be larger in body size, partially because despite shorter growing seasons, they lived longer as a result of delayed maturity. However, discordance with the expected cline was detected between neighboring populations and the variation was sex specific. Adult females became significantly older and larger as elevation varied from 567 m to 1470 m, but the two traits no longer increased with an elevational shift from 1470 m to 1700 m. Adult males at 1470 m were similar in age and size to animals at 567 m but significantly younger and smaller than those at 1700 m. This suggested that sexes could be exposed to different pressures along elevation gradients with females being stronger than males in life history responses to the elevation-induced environmental change. We also showed that factors other than age also contributed to size differences both among populations and between the sexes.