Objective To study on impact of instable noise in workers hearing loss.Method 1456 fracturing workers of oil field were randomly selected as study group,other 351 workers were slected as controls.Other conditions were similar between study group and control group.Level of hearing loss was measured under various intensity of noise in workers with different period of noise exposure.Result High frequency of audition was damaged in workers exposed to instable noise for a long time,positive rate was 35.1％ .Postitive rate for tinnitus and language frequency was 18.9％ and 5.5％ ,respectively,which was markedly higher compared with control group.Conclusion Hearing loss will progress with the longation of working time and increase of noise intensity.