To analyze the internal mechanism between landscape structure and conservation function of lake and reservoir drinking water sources, optimize forest water conservation, and protect water sources, land use/cover information was first obtained on the basis of satellite remote sensing interpretation to calculate the water conservation function index. Later, according to the balance between water withdrawal and conservation, minimum required forest areas of different specific forest types for each reservoir drinking water source were estimated. Finally, multi-dimensional analysis methods were adopted to evaluate the relationships among the water conservation function index, landscape ecological indices, and water quality of the reservoir drinking water sources. The results showed that:(1) the water source conservation function of the 3 km buffer zone of the reservoirs is slightly lower than that of the 500 m buffer zone. (2) Screen riparian forest ecosystems dominated by soft broad-leaved forests, oak forests, hard broad-leaved forests, and bamboo effectively improve the capability of water conservation, meet the requirement of the quantitative relationship and functions of drinking water conservation, rain collection, and protection areas delineating. (3) Regression model equations can be established using the water conservation function index, landscape pattern indices, water resources, water quality, and pollutant discharge. (4) The comprehensive multi-dimensional scale analysis can evaluate the ecological safety and risks of ecosystem stability and water resource quantity and quality of Nanning lake and reservoir drinking water sources. We recommend Nanning City to conduct comprehensive programs and improve the drinking water source environment and ecological system protection and restoration.