Objective To determine the optimal dosage of Folium Artemisiae argyi in air disinfection of animal facility and respiratory irritation to animals． Methods 1. Three different dosages of Folium Artemisiae argyi，1 g /m3，2 g / m3 and 4 g /m3，corresponding to low，middle and high dosage groups，were used in air fumigation disinfection of empty animal facility，respectively． Colony forming units ( CFU) of bacteria was examined before disinfection and 12 hours after disinfection，once a week，for ten weeks． The eligible standard of CFU was ≤30，The eligible rate was calculated in these groups after 10 times of disinfection． 2. Forty SD rats were grouped into 4 groups，the control and 1 g /m3，2 g /m3，4 g /m3 dose groups，each group has a disconnector． Fumigation disinfection was done with 1 g /m3，2 g /m3 and 4 g /m3 Folium Artemisiae argyi in different groups． The lungs of rats were taken out to observe the histopathological injury after 12 hours．Results 1. CFU assay of bacteria was not eligible in all groups before disinfection，but it was eligible in every experimental group after 10 hours disinfection． There were significant differences between the low dosage group and middle，high dosage groups，and no significant difference between middle dosage group and high dosage group． The eligible rate was 80% in low dosage group and 100% in middle and high dosage groups． 2. Pathologicl injury of lungs was observed in all experimental groups． Conclusions The optimal dosage of Folium Artemisiae argyi in air disinfection of animal facility is 2g /m3，meanwhile，it may irritate the respiratory system of experimental animals．