Objective To reproduce bald mice.Methods Bald mice were kept in a mouse box with a filter cap.The box was put into a cabinet for laminar flow in a close system.Results More than 40 pairs of bald mice were reproduced in the past eleven months.On average a pair of bald mice can reproduce 8.90 mice and 3.70 bald mice at a time.Conclusion This is a good way for reproducing SPF bald mice.