Abstract: This article introduces a method determining the equation of penetration curve by multielement regression(MER) in study of double glow discharge plasma metallizing(DGM) and the slope of the penetration curve can be calculated by derivation,the xdy can also be obtained.This method is more reliable and accurate than graphical integration.The variation of diffusion coefficient with the concentration of W and Mo are determined.

Key words: diffusivity, glow discharge, tungsten, molybdenum