The invention discloses erasable ink and preparation method thereof, the ink does not block a pen head, is easy to wipe the ink marks and has better color effect and green environment protection. The ink comprises the following components in percentage by weight: 50 percent-60 percent of micrometer-grade coloring microsphere, 0.5 percent-1 percent of antibacterial agent, 0.3 percent-1 percent of thickening agent and the balance of common tap water or de-ionized water, wherein the micrometer-grade coloring microsphere consists of polymethylmethacrylate or butyl methacrylate coated with pigment or dye, and the grain diameter is between 1 micrometer and 10 micrometers. The ink is better to write and easier to wipe than the pencil without marks, and has the advantages of smooth writing, uniform ink flow, dense and bright color of the ink marks, long time for unbonneting, no pollution and environment protection, waterproof and sunproof written marks and long preservation time and the like.