The top-level governance of mega-scale water infrastructure projects has a profound impact on successful implementation and efficient operation. In modernizing such governance

an accurate understanding and evaluation of its effectiveness is a basic issue. Combining literature review and qualitative meta-analysis methods

the connotation and structure of the top-level governance effectiveness are defined and tested

and its evaluation scale is formulated and tested. The results show the top-level governance effectiveness is involved with a multidimensional concept－including three dimensions: decision-making effectiveness

regulatory effectiveness

and coordination effectiveness. And the defined scale consists of three factors and 16 items and enjoys good reliability and validity. The findings of this study help enrich and improve the theoretical governance system of mega-scale water conservancy infrastructure projects

and lay a basis for formulating targeted strategies and improving governance effectiveness

significant in promoting the management of such projects.