In order to explore the adsorption characteristics of Pb (Ⅱ) and mechanism, polyacrylonitrile was selected as the matrix to be chemically modified with diethylenetriamine (DETA),preferred as an amination reagent,and a kind of polyamine chelating nanofiber (D-PAN) has been successfully prepared. The physical and chemical structure analysis by SEM, BET,FTIR and XPS was performed, and the effects of initial pH value, contact time, temperature, inorganic salt and other factors on the adsorption process of D-PAN were studied.The results show that: amine groups was successfully introduced into three-dimensional network of D-PAN, and multi channel structure is conducive to improve the adsorption properties of D-PAN for Pb (Ⅱ). It had the best static adsorption property at pH 5.0. The maximum adsorption capacity was 1.73 mmol/g obtained by fitting with Langmuir model, and the quasi-first-order kinetic rate constant is up to 0.06 min^-1. Moreover, D-PAN had a significant “salt-promoting” effect, and the adsorption amount of Pb (Ⅱ) in the salt-containing system could be nearly doubled.Combining the results of XPS and DFT, it was found that Pb(Ⅱ) could be removed by chelating with N atoms in polyamine groups to form bidentate and tridentate complexes.Furthermore, D-PAN exhibited excellent structural stability after multiple regeneration. In summary, D-PAN has the advantages of fast adsorption, large capacity and easy regeneration, and has broad application prospects.