Abstract: The brief biography of Karl Ferdinand Braun is recounted. The contributions of his discovery of some crystals conducted electric currents in only one direction,invention of the cathode- ray oscilloscope and improvement the wireless telegraphy are reviewed. The factors of his regarding innovation as his own responsibility,insisting going his owner way,and giving full play to his professional knowledge are summarized.

Key words: Karl Ferdinand Braun, unilateral conductivity of crystal, cathode-ray oscilloscope, wireless telegraphy