In this study, I will try to reconstruct the vowel systems of early stages of Manchu. I will reconstruct, *I and *u­, using the internal reconstruction and the comparative method ; that is based on the evidence from the relics of morphological alternations and on comparing Manchu with other Tungusic languages. I will claim in particular that *u­(that is proto-Altaic *u) can be reconstructed in all phonological environments. This claim will be confirmed from the material in *Ch’??ng-hak-??m, which is the Koran transcription of 18th century colloquial Manchu. Based on the reconstruction of the two vowels, *I and *u­, I will asume at least three historical stages of the Manchu vowel system. Inter first stage, there were 7 vowels, which were divided into two harmony sets. Set 1 (pharyngealized) *I *a *o *u­ Set 2 (non-pharyngealized) *i *e *u In the second stage, there were 6 vowels which comprised 2 harmony sets and neutralized vowel(resulted from the merger of *I into i). Set 1 *a *o *u­ Set 2 *e *u Set 3 *i (neuralized) In the third stage, the era of wirtten Manchu, there were only 5 vowel phonemes, which comprised 2 harmony sets and two neutralized vowels(This stage resulted from the merger of *u­ into u in all environments except when it follows k, g and h). Set 1 a o Set 2 e Set 3 i, u(neutralized)