Abstract Urbanization and global warming have led to more frequent extreme heat events, highlighting the importance of Park Cooling Islands. This study analyzes the cooling effect (PCE) of 50 urban parks in Fuzhou to explore the relationship between park area and cooling effect. The results indicate that there is no simple positive correlation between park area and cooling effect. Specifically, while larger parks may have greater cooling potential, a larger area does not necessarily lead to better cooling effects. The optimal park area for cooling effect ranges from 0.594 to 56 hm2; beyond this range, an increase in park area does not significantly enhance the cooling effect. A low proportion of impervious surfaces, a high proportion of water bodies and vegetation, as well as complex patch patterns can enhance PCE, while excessive edge density and landscape fragmentation can weaken PCE. Based on importance analysis, the external morphological characteristics and internal patch characteristics of parks significantly influence cooling effects. Furthermore, the cooling effect of parks is jointly determined by internal and external conditions, with internal conditions having a more significant impact. Therefore, merely pursuing a “large” park area does not guarantee a “good” cooling effect; instead, greater emphasis should be placed on optimizing park design and layout, simplifying boundary shapes, reducing impervious surface ratios, and increasing vegetation diversity to maximize cooling effects.