The invention relates to a preparation method for an 
oxygen-free 
copper tube for a magnetron. The preparation method is characterized in that the contents of 
copper and silver in a material of the 
oxygen-free 
copper tube is larger than or equal to 99.97%, and 
oxygen content is smaller than or equal to 0.001%. The preparation method includes following process steps: 1, 
smelting: placing number 1 high-purity 
cathode copper in a 
power frequency induction furnace with a core, raising the temperature of the furnace to smelt the 
cathode copper into copper liquid, adding 
lanthanum with the 
mass fraction 
ranging from 0.01% to 0.016% into the copper liquid, keeping the copper liquid at the temperature of 1170 + / -10 DEG , and covering a 
charcoal layer with the thickness 
ranging from 100mm to 120mm and the 
charcoal granularity ranging from 40mm to 60mm on the surface of the copper liquid; 2, upward 
continuous casting; 3, precise cold rolling; 4, recrystallization; 5, cold drawing forming; and 6,finishing. The 
oxygen content is low, electric conduction is excellent, yield is high, and 
metal loss is low.