Estimation of the age of hearing loss diagnosis in every society is recommended to be compared with standard criteria to establish common dirth in management and rehabilitation. This study was conducted in order to determine the age of hearing loss diagnosis with respect to common criteria in Baghche-Ban school of hard of hearing children in Tehran.Methods:  In this retrospective cross-sectional study, 445 children in stages 2, 6 and 10 of Baghche-Ban school of hard of hearing participated. the research was performed by means of the three-stages questionaires that children filled with help of their parents.Results: The mean age of detection of hearing loss  in both acquired and congenital hearing loss in children was 3.5 year-old. while the age in which hearing loss was doubted was 1.8 year-old. In another word the mean age of hearing loss detection decreased as the hearing loss increases(in moderate- profound hearing loss)(P<0.01).Conclusion: among the refrence sources for refering children with hearing loss the least refering was related to physicians. Adversly the mean age of doubting and detection of hearing loss increased in children with family history of hearing loss.(P<0.01). Meanwhile no relationship was detected between the age of diagnosis of hearing loss and the number of deaf members in the family(P<0.02).