Urban blue-green spaces (UBGS) play a positive role in reducing land surface temperature (LST) and mitigating heat island effects in high-dense cities. Urban blue spaces and urban green spaces also have synergistic effects in reducing LST, and the spatial pattern is one of the most important factors of their cooling effect. This study takes Nanjing, China, as study area; seventeen indexes were selected to represent the special patterns of UBGS including area-edge, shape, core area, and aggregation category, and we investigated their relationship with LST. As a result, the synergistic cooling effect of blue and green spaces was identified. The results indicated that: (1) The spatial pattern’s impact on LST has no seasonal difference; (2) Compared to the individual blue and green spatial patterns, the combined spatial pattern of UBGS impact on LST was more significant; (3) Increasing the area and shape complexity, reducing spatial fragmentation can promote the cooling effects of urban blue-green spaces. These results show the correlation between the spatial patterns of UBGS and their cooling effects in both integration and synergy ways, can help governments and policy-makers in deciding on the systematic optimization and fi ne regulation of the UBGS pat tern in high-dense cities, serve as a reference for effective urban planning practices, and promote the integrated development of UBGS.