Otosclerosis is a disease that involves the cochlea and it is developed when the structure ofconnecting tissue in the area of stapedius and the oval window has changed and become unmovable.Consequently, conductive hearing loss and therefore severe sensorineural hearing loss are caused.The causes of otosclerosis have not been discovered yet but many factors impact on this disease. Anyresearch works has not been done on otosclerosis in Mongolia until now and we have conducted theresearch in 2008-2013. Therefore, we aimed to identify the hearing condition after surgery treatmentof otosclerosis.41 patients /47 ears/ who were diagnosed of having otosclerosis with conductive hearing loss, nomiddle ear infection through the comprehensive ear and hearing examinations were selected in thisstudy which was done at EMJJ Clinics between 2007 and 2013. The hearing improvement after thesurgery has been tested under bone and air conduction frequency 500, 1000, 2000, 4000, 8000 Hzand the results before and after the surgery were statistically processed on Excel 2010 and SPSS 17.0software programs. Stapedotomia and Stapedoectomia surgery approaches were applied and afteropening of attics, the hearing bones are palpated and the diagnosis of stapes otosclerosis is confirmedby the surgeon, who removes the stapes. Then a titanium K-piston (prosthese or implant) is thenplaced into this opening and connected to the malleus, or the incus.Out of 41 patients (85.4% female) involved in the study and 36 people had one ear side otosclerosisand 5 people had both ear otosclerosis. After the surgery 25 patients did not have dizziness andvomiting symptoms and 14 patients did not have dizziness with movement after 12 hours, andfor 4 patients all symptoms were disappeared after 24 hours. As for the result from the hearingexamination after 21, 60 days of the surgery, bone conduction was normal, air conduction, andhearing for 32 patients improved completely, and after 120 days of the surgery, the hearing of 33patients improved completely, bone conduction became 2000 Hz at 4000 Hz frequency 12-15 dB,average of air conduction 15,4±10,1 dB, bone-air gap 10,4±3,1 dB for 5 people, and bone conduction2000 Hz-4000 Hz, at 8000 Hz frequency 20-40dB, air conduction became 25-45dB 10,4±5,1db for 9patients and all patients had no hearing loss except for 4 people who still had tinnitus.After surgery stapedotomia and stapedoectomia for the otosclerosis, the hearing improvement was95.2% and it has been concluded that there is full possibility to perform surgeries of stapedotomia andstapedoectomia for the otosclerosis in Mongolian situation.