The invention discloses a composite material with a negative ion releasing function and a preparation method thereof. The composite material comprises tourmaline powder, an auxiliary agent(s) and a macromolecule matrix(es) which are in a weight ratio of 5-20:2-10:70-93, wherein the grain size of the tourmaline powder ranges from 500 nanometers to 3 microns, the auxiliary agent is one or more than two of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, cetyl sodium sulfate, cetyl sodium sulfonate, octaphenyl polyoxyethyiene and cetyl trimethyl ammonium bromide, and the macromolecule matrix is one or more than two of polyethylene, polystyrene, polymethyl methacrylate, polyurethane, polyvinyl chloride and polyacrylate. The preparation method comprises the following steps of: firstly, ball milling the tourmaline powder, the auxiliary agent and water in a ball mill or stirring and shearing in an emulsifying machine; then, drying; adding the mixture into a macromolecule reaction monomer for in-situ synthesis, or mixing the mixture with the macromolecule matrix(es) and then carrying out melt blending after mixing the mixture, so as to prepare a target product. The composite material can automatically release a large quantity of negative ions.