The invention discloses a TNT (Trinitrotoluene)/TNCB (Trinitro-Chlorobenzene) co-crystalized explosive and a preparation method thereof. The preparation method comprises the following steps: I, preparing a TNT-TNCB saturated solution, adding TNT into a crystallization solvent at the temperature of 20 to 50 DEG C, dissolving and filtering to obtain a TNT saturated solution, adding TNCB into the TNT saturated solution for dissolving, and filtering to obtain a TNT-TNCB mixed saturated solution; II, preparing the TNT/TNCB co-crystalized explosive: placing the TNT-TNCB mixed saturated solution into a culture dish, standing in a constant-temperature incubator, evaporating the solvent, sequentially performing crystal nucleus forming, crystalline grain growing, a crystal forming, filtering and drying to obtain the TNT-TNCB co-crystalized explosive. The prepared TNT/TNCB co-crystalized explosive provided by the invention has a low melting point, superior security and excellent detonation performance, can be taken as a novel melting and casting solvent, and has a good application prospect in a high-energy insensitive melting and casting explosive formula. The preparation method has the advantages of simple process, convenience in operation, high security and high product quality.