The transition from checked to unchecked syllables is a crucial phenomenon of sound change in Wu Chinese. This study aims to discover the underlying mechanisms of this evolution, specifically by investigating perceptual age-related differences in Shengzhou Wu. After conducting acoustic and articulatory analyses of checked syllables, an identification task was performed to assess the perceptual importance of F0, vowel duration, and the glottal stop coda in two generations. The results show that older individuals tend to rely more on the glottal stop coda when identifying checked syllables, whereas youngsters place more perceptual weight on vowel duration. Additionally, younger people have a reduced ability to recognize checked syllables, potentially due to their exposure to standard Mandarin. These findings suggest that the glottal stop coda may weaken and disappear before the lengthening of vowel duration in the evolution of checked syllables in Wu Chinese.