Morphological measurements, hematoxylin-eosin staining and Masson staining were employed to determine the age-dependent variations in body size and heart position of the farmed king ratsnakes, Elaphe carinata, under two years old, and in the thickness of epicardial, myocardial, and endocardial layers, and collagen fiber content in those under fifty days old. All statistical analyses were performed using SPSS software packages (SPSS 19.0 for windows). One-way ANOVA and multiple comparisons were used to compare the differences of body mass (BM), total body length (TBL), ratio of BM to TBL, fatness, heart-to-head distance, and heart position relative to total body length, as well as the thickness of epicardial, myocardial, and endocardial layers, and collagen fiber content among different age groups. Results were presented as means ± standard error, and P < 0.05 was considered to be statistically significant. BM, TBL and the ratio of BM to TBL all showed the highest value in the 2-year old group, secondarily in the 1-year old group, and then dropped significantly in the other age groups (Table 1, P < 0.05). However, fatness in the 3-day or 7-10-day old group was significantly higher than that of 1-year or 2-year old group (Table 1, P < 0.05). Heart-to-head distance in the 1-year or 2-year old group was significantly higher than that of any other age group (Table 1, P < 0.05), but heart position relative to total body length showed no significant difference among groups (Table 1, P > 0.05). Within 50 days of postembryonic period, the thickness of myocardial layer was significantly higher in the 50-day old group than that of 3-, 20- or 30-day old group (Table 2, P < 0.05), but no significant differences were found for the thickness of both epicardial and endocardial layers (Table 2, P > 0.05); Collagen fiber content of myocardial layer and heart wall layer in the 50-day old group was greatly higher than that of 3- or 20-day old group (Table 3, P < 0.05). The relative position of the heart did not change significantly, but the thickness of myocardial layer was greatly increased and more collagen fiber content was observed with the developmental process, suggesting that the heart function of Elaphe carinata is gradually enhanced after the first slough and active feeding.