According to Erikson's psychological social development theory, it is the 13-18 years-old youth's main developmental task to solve the ego identity crisis. For the deaf or hard of hearing students educated in regular schools, their development of self-identity under the impacts of hearing culture and deaf culture is more complicated than hearing peers. In this paper the author reviewed researches on deaf identity and discussed under three topics: the aspects of deaf identity, the stages of deaf identity development, and factors affecting deaf identity. It is suggested that more chances should be provided to deaf or hard of hearing students and their parents to understand the deaf culture and sign language; moreover, the deaf community promoters could improve the pluralism of deaf culture.