This paper is an acoustic phonetic description of vowels in Hetang Cantonese, and focuses on the diphthongization of nuclear vowels. Different to the representative dialect such as Guangzhou or Hong Kong Cantonese, the Hetang dialect exhibits its unique characteristics regarding the phonetics and phonology of vowels. A noticeable phenomenon is the diphthongization of nuclear vowels. And, a tetraphthong [uɔᵄi] emerges when the nuclear vowel is diphthongized in a triphthong.