Phosphorus doped PdNi nanoparticles were prepared by one-pot synthesis method，which was care? fully characterized by transmission electron microscope，scanning electron microscopy and X-ray photoelectron spectroscopy methods，showing an ultrafine particle size with a diameter of（4.4 ±1.0）nm. A cyclic voltammetry study demonstrated this material exhibited an excellent electrochemical property with an electrochemically active sur? face area（ECSA）of Pd at 42.11 m2 /g，which was 1.5 times higher than its commercial Pd/C counterparts. Pd/NiP nanoparticles showed a remarkable electrocatalytic dechlorination activity，in which direct electron transfer and indi? rect atomic hydrogen mediated electron transfer two pathways simultaneously occurred during the dehalogenation pro? cess. Meanwhile，voltammetric analyses showed that the electron transfer coefficient（k）was much smaller than 0.5， suggesting the dissociative electron transfer（DET）to the C-Cl bond of 4-CP following the concerted DET mecha? nism. Results indicated that the synergistic effect of trimetallic alloy and the compressive strain caused by the doping of Ni and P atoms markedly promoted the generation and retainment capacities of the adsorbed atomic hydrogen （H*ads）and the absorbed atomic hydrogen（H*abs），and effectively inhibited the hydrogen evolution reaction， thereby enhancing the electrocatalytic dechlorination efficiency. That was advantageous to improving the electrocata? lytic reduction dechlorination efficiency. Electrolyses of 2 mM 4-CP showed that for the material catalyzed by the Pd/ NiP nanoparticles（1.02 mg），87.5% of 4-CP could be completely dechlorinated within 360 min with an apparent rate constant of 0.0057 min-1，demonstrating an excellent dechlorination performance and high stability of the devel? oped material. This work provides a facile strategy for the synthesis of phosphorus-doped bimetallic nanoparticles， which provides an excellent catalyst and an important reference for the future electrocatalytic dechlorination works.