Pd/C catalysts were prepared by introducing complexone (nitrilotriacetic acid trisodium salt, NTA) into Pd precursor solutions, Pd particles were stabilized by the coordination of Pd₂₊ and NTA. Catalysts were characterized by XRD, XPS, TEM and H₂-TPR, and we found that compared with Pd/C catalyst prepared by impregnation method, the average particle size of Pd could by effectively reduced by introducing NTA during preparation. Furthermore, Pd particles could be size-controlled by adjusting the amount of NTA, the average particle size of Pd was decreased from 5.7 to 2.1 nm by increase NTA from 0.5 to 2 times of Pd (molar ratio), but Pd particle size did not continue to decrease by continue increasing the amount of NTA. The best catalytic performance was achieved when the average particle size was 4nm (NTA: Pd=1: 1), conversion was 100% and selectivity of 2,3-dichloropyridine was up to 76.86% after 6 hours of reaction.