Disclosed is a Sn-Zn-Cr alloy lead-free solder preparation method which comprises, (1) preparation of Sn-Cr intermediate alloy, which consists of mixing Cr 0.005-1.5%, Zn 3-12%, and balancing Sn, elevating temperature to above the fusion point of the metal Cr, melting and thermally insulating, fully stirring, charging the residue Sn raw material into the furnace, waiting for dissolution, cooling down, thermally insulating, continuing stirring simultaneously, (2) smelting of Sn-Zn-Cr alloy, which consists of charging the Zn raw material into melting Sn-Cr intermediate alloy, waiting for complete dissolution, fully stirring, thermally insulating, cooling down, thermally insulating while agitating continuously, finally cooling down to room temperature or casting as requirement.