Abstract: Measurement method of permeability of tritium through 305 aluminum alloywith and without preforined film is described. Empirical formula of permeabilityof tritium through 305 aluminum alloys and its preformed film in various surfacecondition is derived. Experimental results show that permeability in plating pre-formed film of aluminum is lower, inhibited permeation effect of aluminum surfacefilm is very obvious in 100-250℃, and the higher the temperature, the morenotable the effect.