Urbanization influences plant phenology. The spring phenology, such as the bud burst and lead unfolding are key biological indicators of plant response to urbanization. However, how plant phenology changes along the urban-rural gradient and whether there is significantly quantitative relationship between phenology and urbanization degree in this transition zone remain unclear. In this study, we used the observed spring phenology data of six common urban woody plant species stand along two urban-rural transects from urban center to rural areas in Shanghai, and the distance to the city center as a proxy for urbanization degree. We investigated the variations of plant bud burst and leaf unfolding phenophases along the urban-rural gradients and their relationships with urbanization degree. The results showed that the bud burst and leaf unfolding phenophases of the six plant species were considerably delayed with the increasing of distance from the city center. There was a linear relationship between the urbanization degree and the phenophases of bud burst and leaf unfolding, respectively. The urbanization degree, i.e., the distance to the city center, could explain 31.5-96.7% of the variations in the phenophases delay. The delay time of the bud burst, the start of leaf unfolding, and the full leaf unfolding of the six plant species were ranged from 3-15 days, 4-13 days, and 3-9 days, respectively. These findings can provide insights for understanding the mechanisms of urban plant phenology and assessing the impacts of urbanization on urban ecosystem services.