Objective To investigate the changes of average body weight gain and serum biochemical indexes of C57BL/6J mice (B6 mouse) and their offspings after frozen-thawed embryo transfer of B6 mice. Methods The mice were divided into three groups in this study. In the experimental group I (E-I, 30 males and 20 females), 2-cell embryos after in-vitro fertilization were collected, and cryopreserved by EFS method, then obtained the offsprings after transplantation of the recovered embryos to oviduct of recipient mice (ICR mouse). In the experimental group II (E-II, 26 males and 17 females), when the mice from E-I grew to maturity, the offsprings were obtained from natural mating of mice from E-I. In the control group (20 males and 20 females), the offsprings came from conventional feeding and natural mating. The three groups of mice were raised to 16 weeks old, weighing the body weight at a regular time intervals, and the serum biochemical indexes were obtained from 16-week-old mice. Then the changes of average body weight and serum biochemical indexes of the mice were analyzed. Results The average body weight of E-I mice was significantly higher than that of control group at each week-age (P<0.01). The average body weight of E-II female mice was significantly higher than that of the control group in 12-16-week old mice (P<0.01), but the average body weight of E-II male mice showed no significant differences compared with the control group except for few weeks. The serum biochemical indexes of E-I and E-II mice were changed in all items except for AST, TP and Ca. Conclusions There are some effects on the average body weight gain and serum biochemical indexes of C57BL/6J mice and their offspings after frozen-thawed embryo transfer.