The present invention provides a functional material, its preparation method, a light guide ink and a light guide plate. The present invention belongs to the display technical field and can solve the problem that existing liquid crystal display devices will produce pollution. The functional material of the present invention includes an inorganic powder whose surface has a modified layer, wherein the inorganic powder includes any one or more of aluminum oxide, magnesium oxide, zinc oxide, zirconium oxide, silicon dioxide, titanium dioxide, boron oxide, diiron trioxide, calcium oxide, potassium oxide, sodium oxide and lithium oxide and the modified layer is generated by a reaction of a dianhydride and a diamine. The light guide ink of the present invention includes the above functional material. The light guide plate of the present invention includes a scattering pattern formed by curing the above light guide ink.
