[Objectives] The present study aims to investigate the effects of water level changes on morphological phenotypes, immune function and stress responsiveness ability in tadpoles of the Dark-spotted Frogs (Pelophylax nigromaculatus). [Methods] The variations in metamorphosis duration, body size and percentage of different subtypes of leukocyte in the circulation blood, as well as the ratio of neutrophils to lymphocytes were measured in the laboratory in the constant water level group and in the rapid, moderate and slow reduction groups at metamorphosis completion. All statistical analyses were performed using SPSS software packages (SPSS 19.0 for windows). One-way ANOVA or one-way ANCOVA and multiple comparisons were used to compare the differences of the parameters mentioned above among different groups. Results were presented as means ± standard error, and P < 0.05 was considered to be statistically significant. [Results] The results showed that the rapid reduction group significantly reduced the metamorphosis duration of tadpoles (Fig. 1a, P < 0.05); the snout to vent length (SVL) of froglets was significantly declined in the rapid reduction group compared with that of any other group (Fig. 1d, P < 0.05), both the body mass (Fig. 1b, P > 0.05) and body width (Fig. 1c, P > 0.05) displayed lower values in the rapid desiccation group, but no significant differences were found among different groups. The percentage of neutrophils was significantly higher in the rapid reduction group than that of any other group (Fig. 3c, P < 0.05), the percentage of monocytes was significantly higher in the constant water level group than that of the moderate reduction group (Fig. 3e, P < 0.05), and no significant group differences were observed for the percentage of eosinophils (Fig. 3f, P > 0.05), basophils (Fig. 3b, P > 0.05) or lymphocytes (Fig. 3a, P > 0.05). The ratio of neutrophils to lymphocytes was significantly higher in the rapid reduction group than that of any other group (Fig. 3d, P < 0.05). [Conclusion] The accelerated water level reduction can lead to smaller froglet individuals, natural immunity represented by both neutrophils and monocytes displayed different patterns, and accompanying with increased stress response ability, which may be detrimental to the survival of froglets.