The newly discovered AxFe2-ySe2 (A=K,Rb,Cs) compounds have attracted great interests because of their parent compounds are insulators instead of being metallic [2-6]. Surprisingly, the bulk superconductivity is found to be coexisting with a unique magnetic structure with a huge moment along the c-axis, which is very different from that of cuprates and regular pnictides, where the AF phase is completely suppressed when superconductivity is optimized.In our recent time-of-flight experiment in Rb0.8Fe1.6Se2, we clearly observed a spin wave up to ~200 meV at 5K. Surprisingly, we found the NNNN exchange coupling J3 is essential for fitting the data with a Heisenberg model, indicateing the possible itinerant feature of this system.To determine whether the system is truely local, we propose to carry out a TOF experiment on MAP/MERLIN at a temperature higher than the Neel temperature.