This paper is a physiological investigation of the vowel nasalization in Chinese by analyzing the nasal and oral airflows for the (C):VN and (C)VN syllables in Shanghai (SH) and Hong Kong Cantonese (HKC). Results show that (i) the degree of nasalization is inversely correlated with the tongue height of the vowel followed by a syllable-final nasal in both SH and HKC; (ii) the duration of nasalization is positively correlated with the advancement of the oral closure for the syllable-final nasal in both SH and HKC; (iii) in general, 10% - 60% of the vowel is nasalized when followed by a nasal ending in SH, except for the schwa, the low-mid back vowel and the low vowel followed by a velar nasal; and (iv) in SH, the schwa, the low-mid back vowel and the low vowel followed by a velar nasal are fully nasalized.