The network of dicumyl peroxide (DCP)/triallyl cyanurate (TAC) crosslinked cis-1,4-polyisoprene was studied by solid-state NMR techniques such as direct-polarization (DP), cross-polarization (CP), and proton T-2 experiments. Line broadening and cis/trans isomerization of mobile carbons were observed in the DP experiments; The information on rigid carbons of network structures was observed with the CP technique, Motional heterogeneity was examined by proton T-2 relaxation experiments. Decreases in long T-2 (T-2L) values from the mobile non-network structures and short T-2 (T-2S) values from the rigid network structures were observed with an increase in peroxide or coagent concentration. The percentage of T-2S in T-2 relaxation, which is related to network density, was observed to increase with peroxide and coagent addition.