Objective To study the subacute inhalation toxicity of Ivermectin TC, and obtain its non-observed adverse effect level(NOAEL).Methods It was performed on the doses of Ivermectin TC 190, 380, 750 mg/m3, the solvent control group (0.03%Tween-80 solution) , the control group and additional group ( there were 6 female and 6 male Sprague-Dawley rats for each group) .The animals inhaled with nose-only exposure for 4 weeks (4 h/d, 5 d/week) .The additional group should be observed another 14 days after exposing.At the end of experiment, the rats were killed, the routine and biochemical detection, the body weight and organ to body weight ratios were all measured.Results In the high exposure group, clinical signs of rats included hair fluffy, dull, salivation, tremors were recorded at the exposure period;in female rats, feed efficiency was decreased, ALT and liver to body weight ratio were increased; in male rats, BUN and ALT were increased, CHOL and body weight for the 4th week were decreased.Histopathological examinations revealed that swelling in the liver cell was seen in some female rats at high exposure group.Conclusion The results suggested that the NOAEL of Ivermectin TC in SD rats was 380 mg/m3(4 h/d for 28 days).