A method for making Nano-scale lead-free solder includes the following steps of: forming a mixture solution Sn-Ag or Sn-Ag-Cu; making NaBH.sub.4, NaOH and alkyl C.sub.12H.sub.25OSO.sub.3Na to a reducing dispersing solution; producing reactant Sn-Ag or Sn-Ag-Cu by means of the oxidation reduction method; and adding 95% ethanol to be mixed, and cleaning the reactant by using a supersonic vibrator for removing boron (B) and sulfur (S) atom which adhere to the reactant, thereby producing the Nano-scale (0.1.about.100 nm) lead-free solder Sn-3.5Ag or Sn-3.5Ag-xCu (x=0.2.about.1.0).