The invention discloses a preparation method of a Cu-Cr-Nb alloy. The preparation method of the Cu-Cr-Nb alloy specifically comprises the steps that a Cu-Nb intermediate alloy, Cr particles and Cu blocks are placed in a crucible and are molten in an induction melting furnace with an argon shield, and then Cu-Cr-Nb alloy ingots are obtained; the Cu-Cr-Nb alloy ingots are placed in a heat treatmentfurnace for solid solution and aging heat treatment, and through machining, the Cu-Cr-Nb alloy finished product is obtained. According to the preparation method of the Cu-Cr-Nb alloy, the Nb element is introduced into the Cu-Cr alloy, so that the performance of the Cu-Cr alloy can be significantly improved. On the one hand, the Nb element generates constitutional supercooling in the solidificationprocess, the alloy structure can be refined, and the fine crystal strengthening function is achieved; on the other hand, in the aging process, the Cr phase and the Laves phase Cr2Nb are separated out, a double-phase strengthened Cu alloy is formed, and the electric conductivity, hardness and heat stability of the alloy can be greatly improved.