Abstract: In order to reveal the contribution and mechanism of three-dimensional (3D) particle electrode to the electrocatalytic reduction of nitrate nitrogen (NO₃-N) in water, a nanometor Pd/Cu-modified bamboo biochar (Nano-Pd/Cu-BC) was prepared using bamboo biochar as template by means of Pd/Cu salt impregnation, roasting and finite surface H₂ reduction. A 3D electrocatalytic reduction system was then established with the 3D particle electrodes to enhance the efficiency of the NO₃-N removal from water by traditional electrocatalytic reduction. The results showed that the prepared Nano-Pd/Cu-BC retained the natural hierarchical porous structure of bamboo, and nano-Pd⁰ and nano-Cu⁰ metal particles were uniformly dispersed on the surface. The 3D electrocatalytic reduction system exhibited a higher removal rate of NO₃-N from water, i.e., the mass catalytic activity of NO₃-N and the N₂ yield reached 0.069 mg/mg and 13.4% in 240 min, which were 5.35 and 2.84 times higher than those of the traditional electrocatalytic reduction system without 3D particle electrodes, respectively. Research demonstrated that the electrocatalytic reduction system with nano-Pd/Cu-BC as 3D particle electrodes can improve the removal rate of NO₃-N and the selection rate of nitrogen generation in water.