【Abstract】Objective To investigate the antioxidant activity of piper longum L extract and its effect on improving LPS-induced hearing loss in rat. Methods The scavenging rate of DPPH free radical from piper longum L extract at a concentration of 0. 05~1. 0 mg/mL, and the inhibitory effect of 25~500 μg/mL piper longum L extract on LPS-induced NO secretion were tested. Twenty four SD rats were randomly divided into blank control group, model group, positive group (hydrocortisone) , and piper longum L extract group with 6 rats in a growp. Except for the blank control group, the model group, positive group and piper longum L extract group were continuously injected 5 mg/mL LPS solution into tympanum for 5 days. The model group, positive group and piper longum L extract group were given normal saline, hydrocortisone (1.81 mg/kg) and piper longum L extract (the crude drug concentration was 1 g/mL) respectively. After continuous gavage lasted for 10 days, the threshold of auditory brainstem response (ABR) , the changes of hair cells in cochlea and the expressions of glutamate, MDA,TNF-a and NO were measured. Results The IC₅₀ of DPPH free radical scavenging of piper longum L was 0.505 mg/mL. The concentration of 25~500 μg/mL piper longum L extract had significant inhibitory effect on LPS-induced excessive NO secretion in RAW 264. 7 cells, with an IC₅₀ of 280.55μg/mL.After continuous garage for 10 days, compared with the model group, the extract of piper longum L extract effectively reduced the ABR value of rats with LPS-induced otitis media in the frequency range of 8， 16 kHz (P<0.01)，and significantly reduced the glutamate, glutamate, MDA,TNF-α，NO factor expression (P<0.05，P<0.01, P<0.001)，and SOD activity increased (P<0.05). Further, piper longum L extract was found to significartly reduce cochlear hair cell loss and swelling, and improved hair cell neatness and structural integrity. Conclusion Piper longum L extract may inhibit the overexpression of glutamate free radicals and inflammatory response in the cochlea tissue, which increase the activity of superoxide dismutase SOD, and has a good effect on improving otitis media and hearing loss.