Disclosed is a moderator for moderating neutrons, including a substrate and a surface treatment layer or a dry inert gas layer or a vacuum layer coated on the surface of the substrate, wherein the substrate is prepared from a moderating material by a powder sintering device through a powder sintering process from powders or by compacting powders into a block, and the moderating material includes 40% to 100% by weight of aluminum fluoride； wherein the surface treatment layer is a hydrophobic material； and the surface treatment layer or the dry inert gas layer or the vacuum layer is used for isolating the substrate from the water in the environment in which the substrate is placed. The surface treated moderator can avoid the hygroscopic or deliquescence of the moderating material during use, improve the quality of the neutron source and prolong the service life.
