Fraser's 2010 cognitive phonology theory believes that pronunciation is a form of behavior and, like other behaviors, stems from concepts. Concepts are abstract motivators of behavior. Words also influence concepts. Each word has a specific meaning, form, and pronunciation, and it is important for the learner to understand its meaning. Therefore, based on this cognitive framework, the formation of concepts arises from the phonological structure in the substrate.. The application of concepts in learning a native language occurs subconsciously at the level of phonemes, allophones, and in the sequence of meaningful elements. In this study, based on data obtained from a field questionnaire and sample study through audio recording, we studied the analysis of vowel errors of Persian-speaking students in the translation field. The statistical population of the study consisted of 80 Persian-speaking learners in the English translation field from the Applied Science University of Tehran province, which was conducted using a descriptive-analytical method. Based on the findings and the above cognitive phonology theory, it can be concluded that an important cause of vowel errors is unfamiliarity with the phonological-phonetic structure and conceptualization of speech as a continuous stream of words and phrases.