The research deals with the simple classification of phonological oppositions in relation to the unstressed vowels and also, the complex classification of phonological oppositions concerning both the stressed and unstressed vowels in the Uzbek language. The purpose of this study is to explore the extent of forming phonological oppositions of Uzbek vowel phonemes in the unstressed position and to classify the identified phonological oppositions. While carrying out of this study, a comparative method was used to compare vowel phonemes with each other, and a descriptive method was used to express their specific features. In the study, simple and complex classifications of phonological oppositions of Uzbek unstressed vowels have been developed. The study concludes that the phonological oppositions of vowels do not lose their significance in the unstressed positions and according to the simple classification, the unstressed vowels have 9 oppositions whose members are differentiated by one phonological feature, and 6 oppositions whose members are differentiated by two phonological features and according to the complex classification, unidimensional, pluridimensional, proportional, privative, gradual, equipolent and constant oppositions of unstressed vowels exist in modern Uzbek.