The digestive tract represents a functional link between energy intake and energy allocation in vertebrates. Its mass and length are highly sensitive to environmental adaption, and is of flexibility. In this paper, sexual and seasonal differences in body mass, snoutvent length (SVL), wet and dry carcass mass indices, as well as wet and dry mass indices, and length indices of total digestive tract and different portions (oesophagus, stomach, small intestine, and large intestine) of digestive tract (Two way ANOVA) were measured in black-spotted pond frog Pelophylax nigromaculata captured in summer (8 males, 8 females, n = 16) and autumn (10 males, 9 females, n = 19) 2012, and in spring (9 males, 8 females, n = 17) 2013, respectively from Liaocheng city, Shandong province, China. If some indices showed significant sexual differences, seasonal variations of those indices for any gender were further analyzed by one way ANOVA. The results were as follows: 1) Body mass and SVL in females were higher than in males, and both were higher in autumn than in spring or summer for both sexes. Wet carcass mass index in males was higher than in females, and was greater in summer than in autumn for both sexes. No sexual and seasonal differences were found for dry carcass mass index. 2) All the wet mass indices of total digestive tract and different portions of digestive tract except for oesophagus wet mass index in females were higher than in males. All the wet mass indices of total digestive tract and different portions of digestive tract except for the stomach wet mass index in spring or autumn were greater than in summer. Both total digestive tract and stomach dry mass indices in females were higher than in males, but not for the oesophagus, small intestine and large intestine dry mass indices. All the dry mass indices did not show seasonal differences. 3) No sexual differences were found for the length indices of total digestive tract and different portions of digestive tract except that large intestine length index in females was higher than in males. The length indices of total digestive tract, oesophagus and stomach in spring and autumn were higher than in summer, but not for small and large intestine length indices. These results indicate that the mass and length of different portions of digestive tract in Pelophylax nigromaculata change with seasons, and display some flexibility characters, which may be related to the functions of digestive organs and diversities of life environments.