The invention discloses a method of directly synthesizing a cubic phase CsPbI3 nanowire. The method comprises the following steps of (1) dissolving cesium acetate into a solvent, adding an oleic acidsubstance as a cosolvent, thus obtaining a cesium precursor after full dissolution, dissolving lead iodide into the solvent, adding an oleic acid substance and an oleylamine substance as surfactants,and performing thermal insulation at T1 to obtain a lead iodide precursor; and (2) adding the cesium precursor in the lead iodide precursor at two times, particularly adding a part of the cesium precursor in the lead iodide precursor firstly, then rising the temperature to T2, then adding the residual cesium precursor in the lead iodide precursor secondarily, and continuously performing thermal insulation to obtain the cubic phase cesium-lead-iodine nanowire. In the method, the whole flow process design of a synthetic method and the like are improved, the cesium precursor is reacted with the lead iodide precursor at two times, and the cubic phase cesium-lead-iodine nanowire can be prepared at a relatively low temperature.