The geo-ecological boundary is a transitional ecotone that differentiates two or more ecozones. Accurate determination of the boundary is crucial for distinguishing and examining the sensitive responses of vegetation and soil to regional climate change and help set guidelines for developing local agriculture-forestry-husbandry production. Qinling Range has been recognized as the geo-ecological boundary between Subtropical and Warm-temperate zones in eastern China, but the precise boundary has been argued for decades with three different viewpoints: in northern piedmont, along the ridge, or in southern piedmont. We conducted comparative analyses using Kira′s Warmth index (WI) and Holdridge′s Potential Evapotranspiration Rate (PER), local vertical vegetation spectrums, ratio of temperate to subtropical floristic composition, and indicator species of agricultural and forestry produces across the whole Qinling Range. Our results indicated: (1), the distribution pattern of WI and PER isograms suggested the whole Qinling Range was within the Warm-temperate zone, (2) floristic compositional analysis showed most of the ten regions investigated in the range were within the Warm-temperate zone with the altitude 1000 m of southern piedmont being the southern edge of Warm-temperate zone, and (3) vertical vegetation spectrums (five on north side and eight on south side, respectively) confirmed that the majority of the range was within the Warm-temperate zone and the contour 1000 m in southern piedmont is the ecological boundary line.