The temperature of some small island cities in tropical country is in the range of 30-34°C. The existence of urban green open spaces is necessary due to its vegetation cover that has the ability of urban cooling in order to reduce the high temperature itself. However, the species diversity of vegetation cover affects the ability of urban cooling of each species. The purposes of this research are to analyse the ability of urban cooling among each species, the status of thermal comfort and the structure of vegetation cover of urban green open spaces, and to devise the most appropriate strategy of vegetation arrangement at the existing urban green open spaces to intensify the ability of urban cooling of the green spaces based on the result of other measured variables. Those variables are the status of thermal comfort with temperature, air humidity, and wind velocity (actual condition of microclimate) and perception of thermal comfort among green space visitors as the parameters; vegetation cover structure with density, frequency, and dominance of species as its parameters; and urban cooling ability with carbon absorption of each species as its parameter. This research used Predicted Comfort Temperature (PCT) and regression equation, indices of density, frequency, and dominance, and the equation of carbon absorption to analyse each variable, respectively. This research was undertaken at two urban green spaces in Tanjungpinang; Laman Boenda Park and Pamedan Ahmad Yani Park. The results indicate that the distribution of trees vegetation cover at Pamedan Ahmad Yani Park is better than Laman Boenda Park’s. Mahogany tree (Swietenia mahogani), cape tree (Mimospus elengi), and banyan tree (Ficus benjamina) are some species with the highest carbon absorption ability per hour while acacia tree (Acacia mangium) has low carbon absorption ability per hour.