The cross-linked poly(ether) electrolytes were prepared by the polymerization of a macro-monomer (tri-acryroyl terminated ethyleneoxide–co-propyleneoxide (EO–PO)) containing LiN(CF3SO2)2 for the three different salt concentrations (O/Li=10/1, 20/1 and 30/1). The self-diffusion coefficients (D) of the anions ( 19 F NMR) measured by the pulsed gradient spin-echo (PGSE) NMR method showed the time dependency. The short-range anion diffusion is faster than the long-range diffusion. The accurate measurement of the diffusion for lithium ( 7 Li NMR) was difficult but the lithium diffusion seems slower than that of the anion. The fast hopping motion of lithium ions is correlated to the segment motion of the polymer. The ion conduction is closely related to the anion diffusion in the longer range. The transport number of the lithium ion can also be estimated from the electrochemical measurements.