The invention belongs to the technical field of materials, in particular to a preparing method of an organic-inorganic fluorescent composite material. According to the preparing method, a mixed solvent homogeneous precipitation method is adopted, the organic-inorganic fluorescent composite material is subjected to one-step synthesis, the technology is easy, the process is easy to control, the cost is low, and large-scale industrial production can be achieved. Due to the fact that the preparing process of the organic-inorganic fluorescent composite material belongs to homogeneous nucleation, the particle size of the material is lower, and the performance is better. The obtained organic-inorganic fluorescent composite material is hopeful to be applied to the field of solid luminescent devices, and the commercial prospect is considerable.