Objective To observe the growth and fecundity of NIH mice under a stable raising condition.Methods 20 cages of mice were randomized for the observation, that is ,10cages each comtained a seed mouse with eight young mice (group 1)and the other 10 cages, a seed mouse with ten (group 2).Results NIH mice produced 10.85 mice on average. The average weight of young mice was 1.74g more with higher survival rate of 8.25% in group 1 than group 2.Conclusion NIH mice showed strong fecundity and fast growth, especially when a seed mouse fed eight young mice.