ObjectiveTo study the dynamic changes of becteria and the dust particles in barrier animal facilities. MethodsTo measure the quantity of falling bacteria and dust particles of larger than or equal 0.3 μm in diameter at different times and in the different functional areas of the barrier animal facilities. ResultsThe quantity of falling bacteria and dust particles were significantly increased in barrier animal room after breeding operation, and was the lowest after spray disinfection. There was a high quantity of bacteria and dust at 00∶00 in the mice and rats breeding room, but was a valley value in the rabbits breeding room at the same time. The quantity of falling bacteria and dust particles was significantly increased in the clean and semi-clean corridor at working time, and was kept a relatively stable level at non-working times. ConclusionsThere are regular changes of the quantity of falling bacteria and dust particles in barrier animal facilities, and these changes are related with animal species, spray disinfection, mobility of persons and materials and operation of animal care.