Sulfur doping can suppress superconductivity gradually in A2Fe4Se5 (A=K, Rb, Cs) materials and turn the material to a semiconducting ground state. Both elastic and inelastic neutron scattering studies are absent on A0.8FeyS2, which may be the real parent compound of ¿245¿ S-based superconductors. With the similar compositions, Rb/CsxFeyS2 are metals, while KxFeyS2 materials are semiconductors. The high temperature resistivity which showed clear kinks from 400 K to 600 K indicates a transition to the blocked AF order similar to the AxFeySe2 system. In this experiment, we would like to measure the possible spin waves which correspond with blocked AF structure and the possible spin excitations stemming from the stripe AF correlations in Rb0.8FeyS2 (y~1.6) at 10 K.