Common carp(Cyprinus carpio) is the main fish species cultured in ponds at high latitudes in northern China, where there are long and cold winters. Common carp reaches market size after a 5-month overwintering period in northeast China. Thus, it is critical to understand the effects of overwintering on the survival and growth of cultured fish. In this study, the growth of Songpu mirror carp (Cyprinus carpio var. songpu mirror) was monitored using passive in- tegrated transponders before and after overwintering. All fish were hatched at the same time and cultured under the same conditions. Morphological indices, liver and foregut histological structure, and biochemical composition of the viscera, muscle, and whole body were analyzed at 125 d (before overwintering), 170 d (beginning of freezing), and 325 d (after overwintering). Furthermore, the correlation between major energetic material at 325 d and overwintering body weight loss rate (WRL) was evaluated. The results showed that body weight (BW), condition factor (CF), visceral-somatic index (VSI), hepatosomatic index (HIS), and intestine-somatic index (ISI) decreased significantly over the entire overwintering period (125–325 d) (P<0.05). Significant degeneration of histological structures for the hepatic and foregut was observed during 125–325 d. Hepatic cells shrank, and the boundaries between hepatic cells were blurred. The abundant hepatic glycogen and lipid stores present before winter disappeared after winter. Foregut diame- ter, villus height, and muscle layer thickness decreased significantly after winter compared with those before winter (P<0.05), and the striated borders of the foregut were clearly atrophied. Visceral fat and hepatic glycogen contents were significantly attenuated at each sampling period (P<0.05). However, whole-body and muscle protein contents only de- creased significantly during 170–325 d (P<0.05). In addition, a significant negative correlation was detected between muscle protein content at 325 d and WRL (P<0.05), but no association was found between visceral fat at 325 d and WRL(P>0.05). Taken together, these results suggest that overwintering led to significant changes in the morphological indices based on common carp BW. Degeneration of the hepatic and foregut histological structures resulted from chronic hunger during the winter. The stages of consuming endogenous energy during the winter varied. Hepatic gly- cogen and fat were used initially during 125–170 d, whereas hepatic glycogen, fat, and protein were used for energy ex- penditure during 170–325 d. Muscle protein content after the winter could be useful as a reference indicator for WRL.