The invention relates to a method for preparing a waste crystal residue/diaminobenzidine type epoxy matrix resin composite material. The method comprises the following steps: drying and pulverizing waste crystal residues, and performing surface treatment with a coupling agent; uniformly mixing waste crystal residue powder with diaminobenzidine type epoxy matrix resin and short fiber so as to obtain a diaminobenzidine type epoxy matrix resin composite material system, filling a mold, and performing heating pressurization curing molding, thereby obtaining the waste crystal residue/diaminobenzidine type epoxy matrix resin composite material. The waste crystal residue/diaminobenzidine type epoxy matrix resin composite material prepared with the method has the advantages that the waste crystal residues are efficiently treated, environmental pollution can be eliminated, wastes can be turned into wealth, resource utilization can be achieved, very significant practical meanings can be achieved for comprehensive environment treatment and the like, and good social benefits and economic benefits can be made.