The invention provides black writing liquid suitable for being written on a matt board and an erasing agent. The writing liquid comprises the components of acid No.3 green, acid fuchsin, a dispersing agent, a stabilizer, a plasticizer, sodium citrate and distilled water. The erasing agent comprises the components of a reducing agent, a complexing agent, a dispersing agent, an antioxidant, a solidifying agent, sodium carbonate and distilled water. The black writing liquid suitable for being written on the matt board and the erasing agent have simple formulas, easily obtained raw materials and low costs. The writing liquid is prepared by an anaglyphic principle, has the advantages of no toxicity, no odor, no generation of precipitates after the writing liquid is stored for a long time and the like, is smooth to write, is particularly suitable for being written on the teaching matt board. The erasing agent can be used for rapidly erasing writing written by the writing liquid, and no writing liquid shadow exists.