An important role of the zinc stearate (ZnSt(2)) activator in the sulfur cross-linking reaction of isoprene rubber is proved by combination of H-1 double-quantum nuclear magnetic resonance spectroscopy and nanomechanical mapping of atomic force microscopy for the first time. The dinuclear-type bridging bidentate zinc/stearate complex (intermediate I) is well dispersed in the rubber matrix to result in the formation of a highly homogeneous network structure by reacting with N-(1,3-benzothiazol-2-ylsulfanyl)cyclohexanamine and sulfur. Upon increasing the concentration of ZnSt(2), the amount of generated intermediate I increases, and consequently, the molecular weight between the constraints (M-c) decreases proportionally. However, a large amount of ZnSt(2) widens the distribution of 1/M-c and decreases the network uniformity. These results are based on the first qualitative agreement between the relative 1/M-c values, and in particular the width of their inhomogeneous distributions, measured by the two techniques. High potential for controlling a network structure in a vulcanizate is shown, where an amount of the generated intermediate I plays a key role.