The invention provides a method for preparing a KNb3O8 nanowire through laser inducing and belongs to the technical field of novel functional materials. A 405nm semiconductor laser is used, Ti and Au are plated on quartz glass before an experiment, and the quartz glass serves as a substrate for growth of a potassium niobate nanowire. Nb2O5 powder is added into a potassium hydroxide solution, the ratio of K to Nb is 50:1, the materials are stirred for 15 min through a magnetic stirrer, and Nb2O5 is fully dissolved; the laser radiation time is 4-12 min. The microstructure is represented through XRD, SEM and other technical means, and it is indicated that the product is the KNb3O8 one-dimensional nanowire of the strongest diffraction peak on a (110) crystal face. Through testing of ultraviolet-visible absorption and photoluminescence performance, it is indicated that the band gap of KNb3O8 is 2.98 eV, and potential blue light luminescence characteristics are achieved. Through control over the laser radiation time, one-dimensional nanostructures with different lengths and thicknesses are generated, and the one-dimensional linear KNb3O8 nanostructures are generated through lasers for the first time.