Abstract: Vowels are the core of English phonetics and play an indispensible role in oral communication. In this study, 160 nonEnglish majors' pronunciation of vowel sounds in basic English words were diagnosed with manual scoring and Praat software. The findings are that: 1) 72. 8% of vowel sounds were pronounced incorrectly; 2) four regular errors occur in their vowel sounds: confusion between long and short vowels, phoneme addition to vowels, grapheme interference, and confusion of schwa /ə/ and lateral /l/. The results indicate that the non-English majors investigated had a poor command of basic English vocabulary, with many pronunciation errors in vowel sounds. Such phenomenon is worthy thinking because poor command of basic words has a serious impact on the development of comprehensive language competence in the long run.