The relationship bettween the existing form and inhibiting behavior of dolecylamme(DDA) On amorphous alloy has been studied by electrochemical measurement, physical test and scanning tunneling microscopy. The experiment shows that there is different relationship between the inhibition concentration and inhibition percentage in different concentration scale. In wDDA=10-6~10-4 concentration range, the inhibition percentage increased strongly with the inhibitor concentration but the increase tendency of inhibition percentage became gently in 10-4~10-3 concentration scale. The adsorption isotherm formula fitting result shows that a typicd mono-molecular layer of DDA was adsorbed on amorphous alloy during 10-6~10-4concentra-tion scale, without any effect from the neighbor inhibitor molecule, but in 10-4~10-3 range the force between the nearing neighbor inhibitor molecule decided the adsorption form. The result from STM and conductivity test indicats that the micelle had formed when the concentration approached WDDA=2.3 X 10-5, the protection effect DDA was prevented because of the forming of micelle.