Abstract: This paper describes the upper and lower heat input limits of EB welding for four kinds of thin sheet materials normally used in aircraft industry. The testing data for the useful range of survey are also provided. The method of approximation to the lower limit for getting a sound weld with full penetration is given. In this paper, we have explained the influence of upper and lower heat input limits on the formation of welding bead and introduced the method of using the curve of heat input range to get the optimum welding parameters. A complete set of turbine guide vanes for a jet engine(75 vanes, 100 welds) has been successfully welded with only one test-weld by making use of the curve of heat input range.