The invention provides burning-free lightweight ceramsite prepared from magnesite waste rock, wherein the burning-free lightweight ceramsite is mainly prepared from the following raw materials by mass: 20-30% of iron tailings, 20-30% of diamond tailings, 25-30% of light burned magnesite waste rock powder, 10-20% of magnesium chloride hexahydrate, and 5-10% of azurite tailings. According to the present invention, the prepared ceramsite has a porous structure on the surface, has large specific surface area and low bulk density, and utilizes a large amount of iron tailings, diamond tailings, magnesite waste rock, azurite tailings and other bulk solid waste, wherein the tailings utilization rate is over 80%, such that the problem that the tailings stacking occupies a large amount of land is solved, the pollution of mine dust to the environment is reduced, the resource utilization of mine waste is achieved, and the good social, economic and ecological benefits are achieved.