The aim of the proposed proposal is to determine the magnetic structure of the Fe moments for the newly discovered superconductor KxFe2-ySe2 using spherical neutron polarimetry at D3 or IN20. Most of the attempts in determining magnetic structure have been focused using powder samples with unpolarized neutrons. The magnetic Bragg peaks overlap with nuclear Bragg peaks implying a k = 0 magnetic structure. The determination of the magnetic arrangement in structures with zero propagation vector is difficult with unpolarized neutrons because of the coincidence of the magnetic and nuclear reflections. Therefore, we propose a spherical neutron polarimetry at D3 or IN20 to precisely determine the magnetic structure.