The increase in the urban population and number of severe weather extremes (including excessive heat) potentially linked to climate change has highlighted the demand of research into assessment and risk mitigation solutions. One of the naturally-based solutions for urban heat stress risk is to enhance the effectiveness of urban greenspaces to mitigate the adverse effects of urbanization and its consequence of urban heat island effect in a sustainable way. The focus of this paper is to investigate the urban greenspaces' features in urban area of Taipei by using high-resolution bands of Sentinel 2 images, which are freely accessible. We present a composite index aggregating four factors including proximity to urban greenspaces, land surface temperature, population density, and land cover to identity patterns of heat stress risk. Results show that urban greenspaces derived from Sentinel 2 images achieved high accuracy with Kappa coefficient of 0.98 and overall accuracy of 99%. Analysis results of heat stress risk indicate that the level of risk is closely correlated with the accessibility to urban greenspaces. It is advised that Taipei City Government and decision makers should take serious measures to enhance the greenness of the environment and effectiveness of urban greenspaces for the benefits of citizens' health and well-beings. Also, it is indicated that Sentinel 2 data are well suitable for not only visualizing the urban greenspaces, but also offering the guidance for landscape planning and management at city scale.