Abstract: According to GB/T 17600.1-1998, it is a cumbersome process to convert the elongation value of steel by continuous checking the formula and the date table. A method of elongation value conversion of steel was introduced through calculation of Excel and the program compiling of visual basic. The customed function was compiled through visual basic, then cited by Excel to convert the elongation value of steel, it isn’t necessary to calculate by checking the formula and the date table.