Mn3Sn has very complex magnetic ordered phase, a clear magnetic phase transition happens at T=~280K accompanied by the vanishing of AHE.For our Mn3Sn crystal grown by flux method, by using polarised neutron diffraction, we found a magnetic reflection splitting below that usually known phase transition temperature T=280K indicating the existence of a new incommensurate magnetic ordered phase in Mn3Sn.So we would like to apply 4 days neutron beamtime at time of flight spectrometer Merlin to re-investigate the evolution of spin waves in these different magnetic ordered phases for better understanding of the exchange interactions and the influence of different magnetic ordered phase on this Weyl system.